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George Washington Flowers 
 A iemorial Collection 
 
 Dl KK UNIVERSITY LIBRARY 
 
 ESTABLISHED BY THE 
 FAMILY OF 
 
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SUMMARY 
 
 COIUSE OF PEBJAMXT FORTIFKATIOX 
 
 AXP OF THF. 
 
 [ttark attb §ifmtt «l permanent P»tb, 
 
 FOR THF. USE OF THE 
 
 cadets of the u. s. MILITARY ACADEMY. 
 BY D. H. MAHAN, 
 
 PROFESSOR OF MILITARY ENGINEERING. ETC., ETC. 
 
 EMTION PRESENTED TO WAR DETARTMFNT, C. S. A., 
 
 BY COL. BLANTON DUNCAN. 
 
 COLUMBIA, S. C. : 
 IOUTB CAROLINIAN |TBAM*POWKB J: 
 
 Ift 
 
TABLE OF CONTENTS. 
 
 PA OB 
 
 System of Fortification Drawing ."> 
 
 Permanent Fortification ;53 
 
 Component Elements of Permanent Works ::i 
 
 OrEN Defences 4'» 
 
 Covered Defences 50 
 
 Communications 67 
 
 Elements of the Plan of Enceintes and Outworks 71 
 
 Outworks am> Detached Works 7:; 
 
 Interior Retrenchments 7s 
 
 I ! A STIONEI) S Y STEM S ~[ I 
 
 Vauban's 1st Method 81 
 
 \ ai ban's 3d Method 88 
 
 Cormontaingne's Method '»•_> 
 
 Methods of the Schools of Mezieres and Metz 99 
 
 v /! B*a Method ' 101 
 
 Cha8SBL01 i-'s Method 1 \\\ 
 
 Haxo's Method i:,:; 
 
 Choumara's Method 157 
 
 Coehorn's Method 166 
 
 T< \ aiu.fi> SYSTEM 172 
 
 < 'a knot's Tenatlled Method 17:; 
 
 Polygonal System 171; 
 
 MONTALEMBI RT's POLYGONAL METHOD 17s 
 
 i: ».< i \ i German Fortifications lg] 
 
 Fronts pi Posen l!tn 
 
 i ndeb in:; 
 
 Wore at Grrmersheim [96 
 
 Ian Ports *202 
 
 Adaptation "i Permanent Fortification to the l 
 
 ORAPHYOA] FEATURES Of FRONTIERS 204 
 
 \ oi the Pr< Fortification 
 
 PRO< 1 [111 l\\ KNTION <•( I IRKAP.M- 
 
 Inm r Irreoui 
 
 Mines 
 
 lck and Defence of ] 
 
SUMMARY • 
 
 OF THE 
 
 COURSE OF PERMANENT FORTIFICATIONS 
 
 ANT) OF TITE 
 
 ATTACK A\0 DEFEXCE OF PERMANENT WORKS. 
 
 SYSTEM OF FORTIFICATION DRAWING. 
 
 I. ..The method now in general use, among military engi- 
 neers, for flclinoat ijilt the plans of permanent fortifications, is 
 similar to the one which had been previously employed tor 
 representing the natural surface of ground in topographical 
 ami hydrographical surveys; which consists in projecting, on 
 a horizontal plana, a) any assumed level, the bounding lines 
 of the surfaces ami. also, the horizontal line- ent from them by 
 equidistant horizontal planes ; the disti these lines from 
 
 the Mil mad plane I numerically in U rms of 
 
 linear measure, as a yard, a I 
 
 2...P lu r? 1:1 \< i . i 
 
 horizontal plane, apon which the linei are project) med 
 
 the . it ip the < 
 
 to which th- g of all I i it arc ; . and 
 
"I I < >Kl 11 1< .VI K'.\ DRAWING. 
 
 as il irapare these distances ^i^i each other, and to 
 
 • nnine the relative positions of the lines. 
 
 ::...]: •■)-. The numbers which express the distances 
 
 from the plane of comparison, are termed refer- 
 
 The unit in which these distances are expressed, is 
 
 usually the Linear foot and it- decimal divisions, 
 
 the position assumed For the plane <>t' comparison* is arbi- 
 trary, it may betaken either-above or below every point of 
 the surface to be projected. 
 
 In the French military service, it is usually taken above; 
 in our own, below tin- surface. The latter seems the more 
 natural ami is more convenient, as vertical distances are more 
 habitually estimated from below upward than in the contrary 
 direction. Each of these methods has the advantage of re? 
 quiring but one kind of symbol to be used, viz: the numerals 
 expressing the references; whereas, if the plane of comparison 
 were bo taken that some of the lines projected should lie on 
 -i«le of it and some on the other, then it would he neces- 
 sary to use, in connection with the references, the algebraic 
 Bymbols plus or mirvu8 % to designate those lines above the plaae 
 from those below it. 
 
 This method of representing objects has^iven rise to a very 
 useful modification of the ordinary one of orthogonal projec- 
 tions on two planes, and has been denominated one j>/<t//e 
 iptvoi geometry } the plane of comparison being the sole 
 plane of projection; the references taking the place of the 
 usual projections on a vertical plane. By this modification'^ 
 the number of lines to be drawn is greatly decreased; the 
 plication of the drawing lessened; the graphical operations 
 required in die solution of problems, presented by the drawing, 
 simplified ; and the relations of the parts more readily seized 
 upon, as the eye is confined to one plane of projection alone. 
 Bui the chief advantage of it consists in .its application to the 
 delineation of objects, like works of permanent fortification, 
 where, from the ureal disparity of the horizontal extent 
 eov< red, and the vertical dimensions of the part s, a drawing, 
 
SYSTEM OF FORTIFICATION DRAWING. 7 
 
 made to a scale which would give the horizontal distances 
 with accuracy, eould not in most cases, render the vertical 
 dimensions with any approach to the same degree of accuracy ; 
 or, if made to a scale which would admit of the vertical 
 dimensions being accurately determined, would require an area 
 of drawing surface, to render the horizontal dimensions to the 
 same scale, which would exceed the convenient limits of prac- 
 tice. 
 
 Taking, for example, an ordinary scale used for drawing the 
 plans of permanent fortifications of one inch to fifty feet, or 
 the scale 1-600, the details of all the hounding surfaces can be 
 determined with accuracy to within the fractional part of a 
 foot; whereas, a vertical projection to the same scale would 
 be altogether too small for the same purpo 
 
 The reference of any point or line of the plane of reference 
 will, therefore, be zero'; that of any point above it will be ex- 
 pressed in feet, decimal parts of afoot being used whenever 
 the reference is not an entire number. In writing the refer- 
 ence the mark used to designate the linear unit is omitted, in 
 k order that the numbers expressing references may not be mis- 
 taken for those which may be put upon the drawing to express 
 the horizontal distances between points. 
 
 The references of horizontal lines are written upon the pro- 
 jections of these lines. All other references are written, as 
 nearly as practicable, parallel to the bottom border of the 
 drawing, for the convenience of reading them without having 
 ti shift the position of the sheet on which the drawing is 
 made. 
 
 4.,.Poon \m> Right Link. To designate the position of a 
 point, PI. 1, Fig. 1, the projection of the point ami it 
 ence are enclosed within a bracket, thu I). This e\- 
 
 prcoae s that the vertical distance of the point from the plane 
 of reference is 88 feet and 50-100 of a toot. The position of a 
 right line, oblique to the plane of re: nated by 
 
 the projection of the lino, and the references of any two of its 
 
 points. Thus, in Fig. 1. the points ./ and t>. upon the projec 
 
s ! ..Kill -li-ATli'N DRAWS*}. 
 
 ti..n of tin- right line, with their respective references, (25,15) 
 and determine the position of the' line with respect to 
 
 the plane of referenc 
 
 When the line is horizontal, or parallel to the plane of refer- 
 . its projection, with the reference of one of its points, will 
 be sufficient to designate it, and fix its position with respect to 
 tin- plane of reference. Thus, in Fig. 1, the reference (25,15) 
 written upon the projection of the line, expresses that the line 
 tg horizontal, and B5,15 feet from the plane of reference. 
 
 5...Fof the convenience of numerical calculation, the posi- 
 tion of a line, with respect to the plane of reference, is often 
 expressed in terms of the natural tangent of the angle it makes 
 with the plane: bul as this angle is the same as that between 
 the line and its projection, its natural tangent can be expressed 
 by tin- difference of level between any two points of the line, 
 divided by the horizontal distance between the points. Now, 
 as the difference of level between any two points of the line is 
 the Bame as the difference of the references of the points, and 
 the horizontal distance between them is the same as the hori- 
 zontal projection of the portion of the line between the same, 
 points, it follows, that the natural tangent of the angle which 
 the line makes with the plane of reference is found by dividing 
 the difference of the references of the points by the distance 
 in horizontal projection between them. 
 
 The vulgar fraction which expresses this tangent is termed 
 the inclination, ot deolimfry of the line. Thus, the fraction 
 1-t; would express that the horizontal distance between any 
 two points is six times the vertical distance or difference of 
 their reference.-: the fraction -$, that the vertical distance be- 
 tween anv two points i^ two-thirds of the horizontal distance; 
 tin denominator of th* fraction^ in all cases, representing the 
 number of parts in horizontal projection, and the numerator 
 tic >;,/■,■■ gtpondmg n utnit ,• of parts in vertical distance. 
 
 When the position of a line is designated in this way, it is 
 
 to he a line whose inclination, or declivity, is one-sixth, 
 
 two-thirds, ten on one, etc., or simply a line of one-sixth, etc. 
 
SYSTEM OF FORTIFICATION DRAWING. 9 
 
 f>..."When the projection of a line is divided into equal 
 parts, each of which corresponds to a unit in vertical distance, 
 and the reference of the points of division arc written, it is 
 termed the scale of declivity of the Inn . In constructing the 
 scale of declivity of a line, the entire, references arc alone put 
 down ; one of the divisions of the equal parts being subdi- 
 vided into tenths, or hundredths if necessary, so as to give the 
 fractional parts of the references corresponding to any frac- 
 tional part of an entire division. 
 
 7... I laving the inclination of a line, the difference of n fer- 
 ence of any two of its points, the projections of which are 
 given, will be found by multiplying the horizontal distance be- 
 tween them by the fraction which expresses this inclination ; 
 in like manner, the horizontal distance of any two points will 
 be obtained by dividing the difference of their references by 
 this fraction. 
 
 To obtain, therefore, the reference of a point of a line, hav- 
 ing its projection, the horizontal distance between it atid that 
 of some other known point of the line must be determined, 
 from the scale of the drawing by which the horizontal dis- 
 tances are measured ; this distance expressed in numbers, be- 
 ing multiplied by the fraction which expresses the inclination 
 of the line, will give the difference of reference of the two 
 points ; the required reference of the point will be found by 
 subtracting this product from the reference of the known 
 point, if it is higher than the one sought, or adding if it is 
 lower. Thus, Let (25,15) be the reference of a known point 
 higher than the one sought ; the distance between the points 
 being 85,57 feet, and the inclination of the line 1-10 ; then, 
 ... ■ l-l" 8,575 will be the difference of reference of the 
 points, and25,15- 8,575 21,575, the required reference. The 
 converse of this show.- that the horizontal distance between two 
 points on this line, who.-'- difference of reference is 3,57*5, will 
 
 be 3,575-j-l-10=85.75 feet 
 
 < 
 
 The true length of any portion of a line between two 
 -idently the hype .t he'iii.-- of I light-angle tri- 
 
 a 
 
LO •" «>l- FORTIFICATION I'KAWIN... 
 
 ther two Bides are the difference of refer- 
 
 ,(1 tluir horizontal distant 
 
 • '..M of a plane Dbliqne to the plane of 
 
 . may be determined tit ln-r by the projections and ref* 
 
 bE points ; by the projections and declivity 
 
 in it oblique to the plane of reference : or by the 
 
 • two or more horizontal lines of the plane, with 
 
 more usual method of representing a plane is by the 
 
 proj n the plane of reference of the horizontal linea 
 
 rmined by intersecting it by equidistanl horizontal piano. 
 
 are termed horizontals of tJu plane^ those usually 
 
 ken the references of which are entire numbers. 
 
 L0...If, in a plane given by its horizontals, a line be drawn 
 
 perpendicular to the horizontals, its projection <>n the plane of 
 
 ■ will be also perpendicular to the projections of the 
 
 horizontals. The angle of tin's line with the plane of reference 
 
 ridently the same as that of the given plane with it, and 
 
 reater than the angle between any other line drawn in the 
 
 plane and the plane of reference. This line is, on this account, 
 
 termed tlo litu of greatest declivity of the plane. 
 
 1 1 — 1 1" the scale of declivity of the line of greatest declivity 
 true ted, it will alone Berve to fix the position of the 
 plane to which it belongs, and to determine the reference of 
 any point of the plane of which the projection is given. For 
 the inclination of this line- and that of the plane are the 
 same; and as the horizontals are perpendicular to the line of 
 declivity, the point where the horizontal drawn 
 through the given projection of ;i point in the plain- cuts this 
 line will determine upon the scale the reference <>t the hori- 
 
 tal, and, therefore, that of the point. 
 i •_'... The inclination, or declivity of a plane with the plane 
 
 nco, may he expressed in the sarnie way as the inclina- 
 tion of its line of greatest declivity. Tims: </ />/<///<> of o?ie- 
 y <■/! mi, , a />/>'/,, of two-thirds^ ex- 
 at the natural tan-cut of the angle between the planes 
 
SYSTEM OF FORTIFICATION DRAWING, 11 
 
 and the plane of reference are respectively represented by tlio 
 fractions J, 20-1 and $. 
 
 13. ..The horizontal distance between two horizontals of a 
 plane, the angle of which is given, can be found in the same 
 way as the horizontal distance between two points of a line, 
 the inclination of which is given, Art. 7, by dividing the dif- 
 ference of the reference of the horizontals by the fraction rep- 
 resenting the inclination of the plane; in like manner the 
 difference of references of two horizonals will be obtained by 
 multiplying their horizontal distance by the same fraction. 
 
 14.. .To distinguish the scale of declivity, PI. 1, Fig. 2, from 
 any other line of a plane, it is always represented by two fine 
 parallel lines, drawn near each other, and crossed at the points 
 of division, where, the references are written, by short lines, 
 which are portions of the corresponding horizontals. 
 
 "With the foregoing elements, the usual problems of the right 
 line and plane can be readily solved. 
 
 PROBLEMS OF THE RIGHT LINE AND PLANE. 
 
 15...Piton. 1, Pi.. 1. Fro. 8, Having the projection* <//<</ 
 two lines thai intersect, to find the angle between 
 //<> in. 
 
 Let <i h be the projection of one of the lines, the referen 
 of two of its points (10,80) and (4,90) being given : c <h the 
 projection of the other line, (10,30) and (5,0) being the refer- 
 ences "f two of its points; (10,80) being the point of intei 
 
 tioll of the tw<. Lii 
 
 Find on each of the lines. Art. 7. a point having the same 
 The line joining these two point.-, will be 
 horizontal, and projected into its true length; taking this lino 
 of the triangle of which the other t are 
 
 respectively the true lengths of the portions of tl iven 
 
 lini b projected betwet □ I L0,8 . 7. the angii 
 
 the vertex will be tl • [uired, 
 
IS -MMI OF FOKTIFTOATIOM OWAW1.N... 
 
 ]»;..' Fro. 4. Through a point , to draw a Jlnepar- 
 
 'tu . 
 I . • be the projection of the poini ; a b thai of the 
 
 :' which the two points (7,0) and (9,0) are known. 
 il'Ii o draw in-- '■ '/ parallel t<> a b, this will be the pro- 
 
 - .it of the required line: and as its declivity is t ho same 
 that <»r the given line, it will be only necessary to set off 
 
 from c toward <L the same distance as between (7,0) and (9 
 tain a point (9,50) as tar above (7,60) as (9,0) is above 
 
 1 7 . . . 1 * i : < . i . . 8, Fig. 5. Through a point in </ plane, to (hum 
 u i',n, in tin j'/ii/o with (i given inclination. 
 
 Lei ocCbe the scale of declivity of the given plane, and a 
 ^iven point; and suppose, for example, that the 
 declivity <-t' the plane is 1-6, and that the declivity of the 
 required line Is L-10. 
 
 1 >raw the horizontal of the plane (5,50) which passes through 
 the point, and any other horizontal as (7,0). The projection of 
 the required line will pass through a, and the portion of it be- 
 tween the two horizontals will be equal, Art. 6, to the differ- 
 of their references, or i.5 feel divided by the fraction 
 which represents the inclination of the required line. 
 Describing, therefore, from a an arc, with this distance a c, or 
 L5-T-1-10 L5 feet as a radius, and joining the point 6, where 
 it cuts the horizontal (7,0), with a, this will be the projection 
 of the required line. 
 
 L8...Psob, 1. IV. L, Fig. 6. Having tkret points of a planej 
 istruct its horizontals and soaU of dscUtoity. 
 
 Le1 a (13,0), I (15,25) and <■ (15,50) be the three points. 
 the lowest with the other two, and construct the scales of 
 declivity of the Lines of junction. Art. »;. The lines joining 
 the same references on these two lines will be horizontals of 
 the required plane. The scale of its declivity will be found 
 by drawing two parallel lines perpendicular to the horizontals, 
 and writing the references pf the points where the scale inter- 
 
 - them. 
 
SYSTEM OF FORTIFICATION DRAWING. 13 
 
 19...Pkob. 5, Pl. 1, Fig. 7. To find the horizontals of a 
 plant pa8S( d through a <jiv< n Une mid parallel to a/mfh, r line. 
 
 Let a 5 and o d be the projections of the two lines. Prom 
 a point (10,0) on c d draw a lino, Prob. 2, parallel to a bj and 
 by Prob. 4, find the horizontals of the plane ol this line and <■ 
 d • these will be the required horizontals. 
 
 20...Prob. 6, Pl. 1, Fig. 8. To find fin horizontals of a 
 plane, tJu declivity of vjhieh is given, and which passes through 
 
 a g'i 'r> n Jim . 
 
 Lei h d be the scale of declivity of the given line, and sup- 
 pose, fbr example, the declivity of the line to be 1-15 and that 
 of the required plane to he 1-12. 
 
 Since the horizontals of the plane must pass through the 
 points of the line having the like references, and as the dis- 
 tance in projection between any two of them, Art 13, will he 
 equal to the difference of their references divided by the frac- 
 tion of inclination of the plane, it follows that, to find the one 
 drawn through I (14,0), for example, it will he simply m 
 sary to describe from any other point, as a (12,0), an arc of a 
 circle, with a radius of 12 feet, equal to the quotient just men- 
 tioned, and to draw a tangent to this arc from 1>. If any other 
 horizontal, as (16,0), is required, which would not intersect the 
 given line within the limits of the drawing, any two points, a- 
 (12,<M and { ]}. hi f,,r example, may he taken as centres, and 
 two arcs he described from them, with radii of 12 :md 24 feet, 
 calculated as above; a line drawn tangent to the arcs will be 
 the required horizontal. 
 
 21 ... I'imc. 7. Pl. 1. Fig. 9. TTa/oing tJu horizontals, or the 
 
 of declivity of two : to find tin ir inU r* et 
 
 .h.in the points where any two horizontals, as (1#,0) and 
 < 1 l.o . in one plane intersect two corresponding horizontals of 
 the other, ami the line bo found will he the projection of tin 1 
 required intersection. 
 
 22.. .When the horizontals are parallel, or when they ar< 
 
 nearly parallel that their points of intersection cannol be 
 
 lily found, the fo method may he taken: I>raw 
 
II • i roM db Lwnro. 
 
 partlle] \h ■ ''. PI. 1. Fig. LO. These may be 
 
 the horizontals of an arbitrary plane having the 
 and (14,0), as the two corresponding 
 hori ich of the given plan 
 
 of the horizontals of the arbitrary plane 
 with those of the given planes will determine two lines, which, 
 being the intersections of the given planes with the arbitrary 
 ill, by their intersection 0, determine a point common 
 to the three planes, and, therefore, a point of the intersection 
 of the two given planes. Assuming any other two parallels, 
 a b, «/' ii. as the horizontals of another arbitrary plane; finding 
 the poinl d common to the three plain's, and joining " and 
 <>' by a line, this will be the required intersection. 
 
 When the horizontals of the two planes are parallel, one 
 point, a> ", will be sufficient to determine the intersection, as 
 projection will be parallel to the horizontals. 
 23...Peob. 8, Pl. J, Fig, 11. To find when a gi/oen lint 
 
 8 -/ givi a plan* . 
 Through any two points of the line, having the same refer- 
 2,0) ill.' 1 ), for example, as two horizontals of the given 
 plane, draw two parallel line-, <i A. a' //. which may be taken 
 a.- tin- horizontals of an abitrary plane. The line of intersec- 
 tion, i" ". oi' this plane with the >/w en plane being determined, 
 by Prob. 7, the poinl " where it intersects the given lino will 
 be the projection of the required point, the reference of which 
 can In- found from the scale of the plane, 
 
 •J l...l'i;. ,:. '.'. Pi . 1, FlG. 12. '/'" drOW from ilijn',1, point 
 
 ,i J*. rj» ndiexdar to << >/'<-, a plan* , itndfina its 1, ngtTu 
 
 Lei '/ il-. 11 ! be tin- given point, and tin- given plane be 
 
 represented 1>\ it- Bcale of declivity. 
 'riic projection of the required perpendicular will pass 
 
 through a Bad be parallel to the scale of declivity of the 
 ■ ii plane. The angle which it makes with the plane of 
 
 the complement of that between this plane and 
 
 tlie given plane; its tangent, therefore, will be the reciprocal 
 of the tangenl 0/ that of the given plane. 
 
SYSTEM OF J'dUl IM< A'l lo.\ IMtAWI.V.. 15 
 
 Drawing, therefore, through a, the line a e parallel to the 
 scale of declivity of the plane, and oonstructing its scale of 
 declivity, Art. 7, tins will be the projection of tjie required per- 
 pendicular. The point 0, where it pierces the given plane, is 
 found by Prob. 8, and its true Length by Art. 8. 
 
 25...Curv<<l and Irr< <jnhtr Surfaces. 
 
 All other surfaces may, like the plane, Art. 7, be represented 
 by the projections on the plane of reference of the curves or 
 lines, cut from them by equidistant horizontal planes, together 
 with the references of these curves; as many of these curves 
 being drawn as may be requisite to determine all the points of 
 the surface with accuracy. 
 
 In the more simple geometrical surfaces, a single horizontal 
 curve, with the projection of some point or line of the surface, 
 will alone suffice. For example, the cone may be represented 
 by the projection and reference of any curve cut from it by a 
 horizontal plane, with the projection and reference of its ver- 
 tex ; a cylinder by the projection and reference of a like curve, 
 with the projection and reference of one of its right line ele- 
 ments; a sphere by the projection ami reference of its centre 
 and that of its great circle parallel to the plane of reference. 
 
 26.. .This method of projection is more particularly advanta- 
 geous in the representation of irregular surfaces, which, like 
 the natural surfaces of ground, for example, are not submitted 
 to any geometrical law, and in solving the various problems of 
 tangent ami secant planes to surfaces of thy character. These 
 surfaces can only be represented by the projection of the hori- 
 zontal curves cut from them by equidistant horizontal pla 
 and by substituting for the zone of the real surface, contained 
 between any two horizontal curves, an artificial zone, suh- 
 jected to sonie geometrical law of generation which shall give 
 an approximation to the real surface sufficiently accurate for 
 
 the object in view. Tie' usual method of doing this i.- to take 
 two consecutive horizontal cu the din f the ar- 
 
 tificial surface of th< B right line SO a- to 
 
 intersect them, and, in each of it- 1 
 
]«; mi.'N DRAWING. 
 
 ieular to the consecutive tangents to one of the our 
 roper curve being usually taken for this last condition. 
 
 If. in 1'!. 1. Fig. L3, for exampl. . etc., arc the 
 
 r the horizontals of a surface, the zone between the 
 ,-ur. i and (7,0) may be replaced by an artificial surface, 
 tin- position of tin- generatrix of which, at any point of the 
 upper curve (7,0), will Ik- determined by constructing the hori- 
 • il tangent at that point, a.- ./. for example, and drawing << 
 i. perpendicular t.. it. and intersecting the lower curve. The 
 position "t" the generatrix •>' b' at any other point a' is con- 
 
 gtracted in like manner. 
 
 8T...T0 obtain any curve of the artificial /cue intermediate 
 to the two directrices, it will he only necessary \<> construct 
 :..!i- of the generatrix, ami to find on these the 
 pointB having the game reference as the required curve. The 
 horizontal of the surface (6,50), for example, will bisect the 
 projections of the generatrix in its various positions. 
 
 I'KOHLKMS OF [RREGU1AR SURFACES AND THE 
 BIGHT LINK AM) PLANE 
 
 28...Pbob. 1". I'i . 1. Fiq. II. Through a given point, in d 
 vertical plan* which intersects a surface, to draw a tang\ nt (<> 
 of i/if, rsi ction oftJu plan< and surfaa . 
 ,50) be t^ie given point, and a b the trace of the 
 plane. The points where this trace intersects the horizontal 
 curves of the surface will be the projections of points of the 
 carve. 
 
 L' ; any arbitrary line. ;•- ,/ ,-. be now drawn through <i. ami 
 cale of declivity he constructed; and let the horizontal 
 Lines oe drawn between the points having the same references 
 on ./ c and a b where the tatter cuts the horizontal curved. 
 Tin intals will generally make differenl angles with a 
 
 id the o: . ." . which makes the smallest angle with 
 
 it. toward the descending portion, will determine on the curve 
 
SYSTEM OF KoKTIi li ATION DKAWIM,. 17 
 
 the tangential point. To show tin's, construct the scale of de- 
 clivity of the line thus found, of which a (6,60) is the projec- 
 tion of one point, and (7,0), on a &, the tangent point, another. 
 This is most readily done, by drawing through the points 
 (10,o), (O.oi, etc., of a c. lines parallel to the horizontal (7."', 
 and finding where they intersect a b, in which the required 
 tangent will be projected. Ootnparing now the references of 
 the points on the line just found, and assumed as the required 
 tangent, with the references of the points of the curve having 
 the same projection, it. will at once he evident that these two 
 lines have only the point projected in (7,0) in common, and 
 that every other point of the right line is exterior to the curve, 
 and, therefore, this line must be tangent to the curve at the 
 point determined as above. 
 
 29 m .Pb< >b. 1 1, 1 ) l. 1 . Fio. 1 5. To construct tin > A m< tits of a 
 
 with a given vertex which .shall envelop a given surface. 
 
 Let (10,0), etc., be the horizontals of the given surt'aee; and 
 
 .") the position of the vertex of the cone. 
 From </. draw a b, a b\ etc., as the traces of vertical planes 
 which pass through the vertex and intersect the surface. 
 Construct, by Prob. 1", the tangents, from a to the curves cut 
 from the surface by the planes a b, etc., These tangents will 
 be the required elements. 
 
 30...Pkob. L2, l'i.. 1. Fio. L6. To find the curve of inten 
 
 oeloping a given surfaa by a horizontal plane. 
 Having found, by J'roKs. 11 and ll\ the elements of the 
 d constructed the scale of declivity of each one, by 
 joining the points 0, d a", having the same reference as the 
 • n horizontal phi: \"i for example; tin.- will form a 
 
 continuous line md'don, which will be the projection of the 
 points win re these elements pierce the given plane, and, th< 
 the projection of the required intersection. 
 31...P&OB. L8, l'i. 2, I io. 1. .1 limited extent oj 
 
 ii< I i/n I thin 
 
 'ones may h passed through thu 
 
 all th 
 
 3 
 
18 SY8T1 V Q [< All-'N ni.ww WO. 
 
 .veil point; ' l".' • tc.j the hori- 
 
 [veu surface, tin- limits of which are the Bector 
 
 tained within the arc II I> ( . and the two radii a B and a 
 
 • 
 Taking a -as the vertex of a cone which shall envelop the 
 . -In- elements <»f this cone can he fonnd by 
 :i and 12. Any plane that can be passed tangent t<> 
 
 this Cone, and which shall not intersect the surface within the 
 
 • limit-, will satisfy the conditions of the problem. 
 Prom the position of the rertex of the cone with respect to 
 tin- surface, it will be Been thai a horizontal plane, passed 
 
 through the rertex, will cut from the coin- two horizontals a b\ 
 
 and ■' I-" (8,0) [the firet of which will he tangent to the hori- 
 zontal curve (8,0) of the surface, and the second a h" will 
 pierce the Burface, where the Limiting arc B D C cuts the 
 6 horizontal curve]; and that all the elements projected 
 within the angles B 'i V and Co />' will lie below the horizon- 
 tal plane (8,0). Now. if the elements within these angles be 
 prolonged beyond the vertex, they will form two portions of 
 cones having the same elements as the portions below the 
 rertex; and it is evident that any plane passed tangenl to the 
 
 lower portion, as V -/ A', within one of these angles; will leave 
 
 this portion below it. and 0"' corresponding portion, formed 
 by the prolonged elements, above it: and. in order that this 
 plane -hall satisfy tin- conditions of tin- problem, it must also 
 Leave the portions of the cone wiflmn the angles V .& V\ and 
 V* a O, also below it. The same reasoning applies to planes 
 passed tangenl to the portion.- of the cone within each of the 
 other two angles. It is. therefore, evident that a plane, which 
 
 shall satisfy the conditions imposed, must leave all that por- 
 tion of fhe cone which lies above the horizontal plane (8,0) 
 through the vertex below it, and all the prolonged portions 
 corresponding to the portions belo\tf the plane (8,0) above it. 
 To find any Buch plane, let the cone be intersected by a 
 
 horizontal plane, a- (9,0), !>v Prob. L2. This plane will cut, 
 from the portion of the cone within the angle V a h", a curve 
 
SYSTEM OF. FORTIFICATION DRAWIM.. 19 
 
 of which n o n' is the projection; the two extreme points of 
 this curve, within the limits, being at the points where the 
 horizontal (9,0) of the surface elite the limiting arc; it will also 
 cut, from each of the prolonged portions, a curve, the one in r, 
 and the other m r' ; the extreme point m of ;// /' being on the 
 prolongation of the extreme elements C; that m' of the other 
 on the extreme clement a B, on the other side, prolonged. 
 Having obtained these three curves, let tangent lines be drawn 
 from the points m and m' to the curve n o W. A plane passed 
 through either of these tangents and through the correspond- 
 ing element of the cone a .?, or a *', drawn through the tan- 
 gential point, will he a tangent plane to the cone; and as 
 either of these planes will leave the curve n o n! on one side of 
 it. and the two curves //> r and ml r' on the other, it will leave 
 all tlic portion Of the cone corresponding to the first curve 
 below it, "and the portions corresponding to the other curves 
 ahove it; and will, therefore, satisfy the required conditions. 
 The same will hold true for any tangent plane to the cone 
 along any element drawn between the points s and «'/ since 
 the tangent drawn t<> any poinl of the enrve n <> n, between 
 the |" lint.- a and .*>', will leave this curve on one side of it, and 
 the other two. /// /- and ml r\ entirely on the other. 
 
 The two horizontal elements, a V and a b" of the cone, 
 will be parallel to the asymptotes of the curve n o ■/ \ 
 and their lines of prolongation beyond the vertex will be par- 
 allel, in like manner, to the asymptotes of the two curve.-, m 
 r and //'' / ■'. 
 
 .Pros. 14. Pl. 1. l'i'.. L6. Through a gvoe* line, topati 
 a flam tc/ng< ni t 
 
 1st. Let a & be the projection of the given line, and (10,0), 
 (9,0), etc., the horizontals <>t the surface. From the point! on 
 the line, as (10,0), etc., draw lines tangent to the horizontal 
 curves having the same t nt which rua 
 
 with the projection of the line the least sngle toward the den 
 ding portion will, with the line, determine the requ 
 
 pla: 
 
SYSTEM Ol I "Ki!M(\\ i [OM DB A\\ KNO. 
 
 • 
 
 For, let the horizontal tangent (10,0) be the one which 
 
 nukei with <t 5 the least angle ; from the other points, (9,0), 
 etc., of a £, draw Line* parallel to the tangent (10,0) ; th 
 lines will lie in the plane thai contains this tangent and ab, 
 
 and will be horizontals of this plane; they also lie respectively 
 in the planes of the horizontal curves (9,0),. (8,0), etc. ; but, 
 since thej fall exterior to the curves, it follows that their plane 
 lies exterior to every horizontal curve of the surface, ex- 
 cept at the curve I 10,0) when- it touches the surface at the 
 point of contact of its horizontal (10,0) with this curve. 
 
 I'd. When the line a 5, PI. L, Fig. 17, is horizontal, let tan- 
 gents be drawn to the horizontal curves and parallel to a b. 
 These tangents may be regarded as the elements of a cylinder 
 which envelops the surface, the tangent plane to winch will 
 be tangent to the surface'. To find the element of contact of 
 the plane and cylinder, let the cylinder and given line be in- 
 d by an arbitrary vertical plane, of which o d is the 
 trace. From the point 0, where the line pierces this plane, let 
 a tangenl line be drawn to the curve cut from the cylinder by 
 the plane, by Prob; 10. The point of contact will determine 
 the position of the element of the cylinder along which the 
 j. lane, through a &, will be tangent; since the tangent to the 
 curve projected in <L With the line a b, will determine the 
 tqpgent plane to the cylinder. 
 
 :;d. When the line a &, PI. 1, Fig.18, is so nearly horizontal 
 that tangents cannot be drawn from its points, within the lim- 
 it.- of the drawing, to the horizontal curves, let any point of 
 the line as (7,0), he taken as the vertex of a cone enveloping 
 the surface; a plane passed through the line and tangent to 
 the cone will be tangenl to the surface. 
 
 Find, by Probs. L0 and 11, the curve m r n cut from this 
 cue by the horizontal plane (8,0); from the point (8,0) of a 
 I) draw a tangenl to this curve. This tangent, with the line a 
 />. will determine the required plane, 
 
 Peob. \'k I'i.. 1, Fi... lit. To Jin <7, <i ]>]>rt ->ximately, the 
 ,1 //•/>< r< <t <//'r, a right Hue pierces a surface. 
 
SVSTKM OF FORTIFICATION DKAWINC. 21 
 
 Let (8,0), (9,0), etc., be the horizontals of the surface, and 
 d f the scale of declivity of the line. Through any two 
 points, as'a (9,0) and c (8,0), draw two parallel lines, as am 
 and c n, which may he taken as the horizontals of an arbitrary 
 plane passed through the given line. Joining the points tn n 
 where the horizontals of the arbitrary plane intersect the cor- 
 responding horizontals of the surface, this line m 11 will be the 
 approximate intersection of the plane with the zone of the sur- 
 face between the horizontals (8,0) and (9,0), and the point 0, 
 where m n intersects d /, will be the approximate point re- 
 quired. 
 
 34:...Prob. 16, Pl. 1, Fig. 20. To find tin- intersection of a 
 plant and surface. 
 
 Let (10,0), (9,0), etc., be the horizontal curves of the surface, 
 ef the scale of declivity of the plane. 
 
 Draw the horizontals of the plane having the same refer- 
 ences as the horizontal curves; the points of intersection of 
 these lines, in their respective planes, will be points of the 
 required intersection. 
 
 When it is desired to find a point of the curve of intersec- 
 tion intermediate to two horizontal curves, if the reference of 
 the required point is fixed, it will be necessary to construct, 
 Art. 27, the horizontal curve of the surface, and the horizontal 
 of the plane having this reference; their intersection will give 
 the required point. If the reference of the required point itf 
 not fixed, draw any generatrix, as a c, of the zone on which 
 the required point ia to be found, and, by Prob. 8, Fig. 11, find 
 the point, U ". where '/ C pierces the given plane ; this will be 
 th<- required point. 
 
 ... Application "i Pbecedhtg Pboblemb. The following 
 problems will aid as illustrations of the preceding subject in 
 its application to the determination and delineation of ] 
 and inrfai 
 
 S...Pbob. 1, Pl. -. Fio. 3. 2% />/>/,< . r },\ 
 
 tin anterior Inn and seal* of declivity of its ten ino 
 
 I riruct tin ]>/<(/<< of tl 
 
M II 1( \TI<'N UKAWLNl. 
 
 'nclinati g //<- rampart-el 
 
 lead < the plain of silt to the terreplein. 
 
 I . • : i.' and ft 76,0) be the references of two points on 
 tlir exterior line of the terreplein, and m n its scale of de- 
 clivity : let the rampart-elope be 3-2; the declivity of the ramp 
 l :-. its width 4.80 yards; and the plane of site bo horizontal 
 and at the reference (60,0). 
 
 The fool of the rampart-slope lying in the plane of site 
 will be horizontal, and will be determined, Prob. 6, Fig. 8, by 
 finding the line of the slope at the reference (G0,0). 
 
 Baving the two bounding linos of the rampart-slope, the inner 
 line, o '/. "l" the ramp is constructed by assuming a point, c, on 
 the t"""t of the rampart-slope, as the point of departure, and 
 determining the line of l-:». drawn from c, on the rampart- 
 slope, by Prob. 3, Fig. ■>. Having found this line, which is 
 also the Line of greatest declivity of the ramp, the exterior 
 line, i f y of the ramp is. drawn parallel to it, and at a distance 
 4.80 yards, equal to the width assumed for the ramp. The 
 horizontals of the ramp will be perpendicular to these two 
 lines. The foot of the ramp, o <\ will be a horizontal line 
 drawn through the point of departure* The top of it, d f\ 
 will be determined) by Prob. 7. Fig* '.'. by finding the intersec- 
 tion of the ramp and the terrepleinj one point of which will be 
 the point <l (76,80), the intersection of the inner line of the 
 ramp and the interior line of the terreplein. 
 
 The ramp i> terminated on the exterior by passing a plane 
 through it.- exterior line < /', having the same slope as the ram- 
 part-elope. This plane will interseel the plane of site in a line 
 parallel to the foot of the rampart-slope, and the, terreplein in 
 one parallel to the exterior line of the terreplein. 
 
 87. ..Picon. IS, Pi.. 2, Fi<;. .'i. Having given the lines of the 
 ■ r i of a work, and the scales of declivity of the planes of 
 Uerior crest and terreplein, to determint the lines and sur- 
 abarbetU in its salient for jwp guns. 
 
 Let a b be the scale of declivity of the plane of the interior 
 it, which, as the terreplein is parallel to the plane of the 
 
SYSTEM OF FoKTlI'iCATKiX DKAWI.No. 23 
 
 interior crest and 8 feet below it, estimated vertically, will also 
 serve as the scale of declivity of the tcrreplein, by subtracting 
 8 feet from the references of the former to obtain the corres- 
 ponding references of the latter. Having constructed a pan- 
 coupe of 4 yards in tbe salient, find the intersection of the top 
 surface of the barbette, which is horizontal and assumed on 
 the drawing at the reference (82,75), with the planes of the 
 interior slope, this intersection will determine the foot of the 
 genouillere of the barbette. From this last line at the pan- 
 coupe set back along the capital a distance of 8 yards, and 
 from the extremity of this line draw a perpendicular to the 
 interior crest of each face. The pentagonal figure thus marked 
 out will be the space for the gun in the salient. From the 
 foot of each of the perpendiculars set off along the faces dis- 
 tances of 12 yards, for the lengths along the interior crests to 
 be occupied by two guns on each side of the salient. Setting 
 back from the extremities of these two last distances, set off 
 perpendiculars to the interior crest of 8 yards, and drawing 
 lines through the extremities of these perpendicular parallel 
 to the interior crests, they, with the two perpendiculars, will 
 mark out the exterior bounding lines of the barbette. By 
 passing planes of 1-1 or 45° through these exterior lines, and 
 finding, by I 'rob. 7, Fig. 9, their intersections with the tcrre- 
 plein, these lines will be tin' t'oot of the barbette-slopes. A 
 ramp, having a slope 1-6, Leads from the terreplein to the top 
 of tin- barbette ; the width of this ramp is 8.30 yard-, its inte- 
 rior line in projection being on the prolongation of the foot of 
 the banquette-slope. Tin 1 ramp is terminated by aide-slopes of 
 
 1-1, tin- intersections of which with the terreplein ami the 
 
 slopes of the barbette and banquette are found by Prob. 7, 
 :*. The fool of the rani]., or it> intersection with tlie 
 
 terreplein. is also found by tie- game problem. 
 
 A- the top surface of the barbette is horizontal, it may !»«• 
 necessary in some cases to make the interior crest, along the 
 
 barbette, also horizontal, in which case the superior slope of 
 
! ..Kill l< All'i.N DBAWINQ. 
 
 along the barbette being higher than the rest of 
 
 it. the t\v.» pUnee will be connected by a plane of 4-.*)°, as at c. 
 
 B8...Pbob. L9, I'i. -. 1'i'i- T To determine //>• hounding 
 
 ip leading ttp an irregular surface, and so 
 
 ed that i r centrt line shall nearly ooincidi with the 
 
 ■ "face. 
 
 Lei 8, . 9,0), BtC, 1"' the horizontal curves of the surface, 
 
 ami let i the point of departure or foot of the ramp. 
 
 Assuming the declivity of the ramp !-'.», for example, from a, 
 
 with a radius of 9 units, describe an arc and join by a right 
 
 line the point b where it cuts the horizontal (9,0) with the 
 
 point Repeat this construction, from b to c, on the horizontal 
 
 ( 10,0); and BO "H to the top, ' . or point of arrival. The broken 
 
 line aJh&d-e will he the projection of the axis. But, to avoid 
 
 the angular changes of direction, tin' .straight portions of the 
 1 1 1 : i \ he connected at the angular points, by setting off 
 from A, for example, the equal distances l> a, b (f, and connect- 
 ing these points by an are of a circle tangent to the straight 
 portions. The same construction being repeated at the other 
 angular points, the broken hue will he replaced by the sinuous 
 line ,/ ,[' r\ etc., as the axis. Saving determined the axis, the 
 exterior and interior lines of the top surface are drawn par- 
 allel to the axis, and at a distance from it equally to half the 
 assumed width of the ramp. From the position of the axis, 
 the exterior half of the ramp will be in embankment, and the 
 interior in excavation. To determine the side-slopes of the 
 embankment, pass planes through the Btraight portions of the 
 exterior edge of the ramp, and lind, by Prob. 6, PI. 1, Fig. 8, 
 the horizontals of these planes, and, by Prob. 1G, Fig. 20, the 
 intersections of these planes with the irregular surface. The 
 plane Burfaces of the Bide-slopes thus determined, are con- 
 nect. ■■! by curved surfaces whic-h pass through the curved lines 
 of the exterior edge. These surfaces may be determined as 
 follows : Take, for example, the point n at the foot of the 
 plane side-slope J, where it cuts the radius prolonged, of the 
 arc a! d ; and the point on the radius through d where it 
 
BYBTBM of fortification du.wvim,. 25 
 
 cuts the foot, of the plane side-slope B. The lines, of which 
 n v and o u are the projections; will evidently have the same 
 inclination, and they may be assumed as the lines of junction 
 of the plane-slopes A and B and the curved side-slope x s . 
 This curved sidenslope may then he generated by the-motion 
 of a right line, which has the top line of which v u is the pro* 
 jectiou for its directrix, whilst in its motion it makes a con- 
 stant angle with the plane of comparison, ami its projections 
 are constantly normal to the arc v u. From the construction 
 comprising these conditions, the foot n o, of the curved portion 
 x, of the side-slope is determined. The same constructions are 
 repeated to obtain the portions, C, of the plane, and y z of the 
 curved side-slopes, with the line m-?i-o-j)-q-r-s the foot of these 
 slopes. 
 
 The side-slopes of the part in excavation A\ B\ C and 
 «f y with the line m' -ri -o' -p' -(/ -r' , are determined by like con- 
 structions. 
 
 The portions of the top surfaces of the ramps, bounded by 
 the arcs of circles, are helicoidal surfaces, of which the axis is 
 the directrix and the plane of comparison the plane director. 
 
 The curved surface side-slopes are also evidently helicoidal 
 surfaces, the directrices of which are the curved lines above 
 mentioned; and the vertical lines through the centres of the 
 arcs the projections of these lines. 
 
 Remabkb. In the Figure, the declivity of the side-slopes of 
 the embankment is one-half the excavation. The declivities 
 of the curved portions of the top are greater than thoa 
 plane surfaces, the difference depending on the angle between 
 the straight portions of the a] 
 
 S9.../'/"/i, Section, Elevation and Profile. 
 
 In delineating permanent fortifications, horizontal projec- 
 tions and horizontal sections, both of which go under the gen- 
 era] name wplans, are used to represent the relative positions 
 of the parts and their dimensions horizontally, tntei 
 of the part- by vertical planes D any required direction, 
 
 and termed . .-di^v the relative j and dinien- 
 
 4 
 
. , !i 1. Vll-'N l»i: A WIN... 
 
 all the parts in the plane of section, both horizontally 
 jections on :i vertical plane, termed sleva- 
 nt tin- forms of the exterior surfaces 
 projected and their relative positions vertically. 
 /' • • an ctions made by vertical planes passed perpen- 
 dicular i" the horizontal projections of the interior crests of 
 the parts where the profiles are taken; they give the vertical 
 and horizontal distances between the points in tli<' plane <>t' the 
 profile. Usually, s profile only shows the bounding lines of 
 the parts intersected, thus presenting nothing more than an 
 outline of the parts. 
 
 In giving a horizontal section, it is customary not only tp 
 delineate the forms Contained in the plane of section, but to 
 project upon this plane all the parts which are Been below it, 
 ami in some cases parts which are covered by others, tin- (Jut- 
 lines of tin- latter being shown by broken, or dotted, lines, to 
 distinguish them front the outlines nt' tin- parts in view, for 
 which full lines are used. A like method i- sometimes em- 
 ployed in sections, the visible parts beyond the plane of 
 tit. n being projected upon it ; thus combining an elevation ami 
 in in the Mime figure. 
 For the perfect comprehension of a fortification, not only 
 will all of the foregoing modes of delineation be requisite, hut 
 the references of all the points and lines, as well as the verti- 
 cal and horizontal distances that determine, the relative posir 
 of the points, must he carefully written on each figure. 
 In PI. :;. Figs. 1. 2, ::. which show the plan, section and 
 elevation of tin- end of the face of a work, an illustration i$ 
 given of the usual manner in which such drawings are made; 
 
 and the same system will he pursued in the figures which fol- 
 low 1 ! 
 
 \fi... Observations <<n tin iMa/M for obtaining accuracy in 
 drawings. 
 
 The first requisite in all drawings intended to represent not 
 
 only tin- outline of the forms of objects, hut to afford the 
 mean- of determining the exact dimensions of each part, is 
 
3V8TEM OF FORTIFICATION DBAWINO. 27 
 
 minuU accura<nf, both in the geometrical constructions, and in 
 writing down all tetters and numbers which serve either as 
 references or to give the dimensions, 
 
 To attain this end, so tar 88 regards the geometrical part, 
 judgment is to be exercised in the selection of the means for 
 establishing on the drawing the positions of the various points 
 which are either given or to be found; as one method, 
 although in theory as correct as some other, may not, in prac- 
 tice, be found to yield as satisfactory results. Attention to 
 the following remarks will serve both to illustrate the mean- 
 ing here intended, and to give some simple practical methods! 
 
 1st. In setting off several distances along a line, whether 
 equal or unequal, the most accurate method is to commence by 
 first setting off the entire distance, and then the several parts; 
 taking care to verify, from the scale, the aggregate of the 
 ral partial distances; thus, in the annexed PI. 2, Pig, 5, 
 where the aggregate of all the partial distances is 60.83 feet, 
 commence by setting off the entire distance ''»'»'. 33 feet; next 
 tH f.33, which is the sum of the two distances, 20' and c5<»'.33, 
 then verify the remaining K»' by the scale. 
 
 2d. When a distance to be set off 18 so small that it cannot 
 be laid down with accuracy by the points of the dividers, the 
 >wing method may be employed: sit back, from the point 
 from which the required distance is to be set off, any arbitrary 
 distance, then Bet forward, from this last point, a distance 
 equal to the sum of this arbitrary distance and the one re- 
 quired; thus, in PI. 2, Pig. 6, where 2' is to be set off from a 
 toward < . -< I back from <> say 30' to A. then from h 88* I 
 
 8d. In setting off a point at a given perpendicular distal 
 from a line, instead of drawing a perpendicular, in the first 
 place, to tlic line, it will mostly be found more speedy, and 
 more accurate, to take off from the scale the given distance, in 
 the dividers, and. Betting one point on the paper, bring the 
 
 r so that the ar<- • .. scribed by it. with the g\\ 
 as a radius, shall be tangent to the line ; thus, in i' ..7. 
 
 wishing ffc at 20* from >> /', take 2C in the divider.-. 
 
OF FOKTIFH \'I KMJ DRAWING. 
 
 . find where one point must be placed bo that 
 
 the other d( an arc will touch a h. This method will 
 
 d convenient in drawing a parallel to a line at a given 
 
 diatance from it by Betting off another point in the same way. 
 
 4th. In Betting off several points, for the purpose of drawing 
 
 • ral parallels to a given line, as, for example, the lines 
 
 which bound the planes of a parapet, it will be found most 
 
 - dy and accurate to draw upon a Blip of smooth thin paper 
 
 two lines perpendicular to each other; mark on one of the 
 
 lines the reaped □ distances from the other; then cut 
 
 tin- paper close to the line along which the given points are 
 
 marked off; so that, when the strip is laid upon the drawing, 
 
 the other line marked upon it being Laid upon the line of the 
 
 draa ing to which the parallels are to be drawn can be pricked 
 
 «.H". either by a sharp-pointed pencil, or in any other way. In 
 
 PL -. 1 "'L r . s . a b i> the line of drawing; .1 the Btrip of paper, 
 
 . etc, the distances at which the parallels are to be 
 
 drawn from a //, marked oil' on the edge of A perpendicular to 
 
 the line /', which line, when .1 is laid on the drawing, should 
 coincide with </ />. If the line ,/ l> is sotnewhal long, it will he 
 heti< r to -et off these |<oiut> near each of its extremities than 
 to draw the parallels by aid of the ruler ami triangle. 
 
 5th. When a point 18 to he constructed by means of the in- 
 
 ten i two Lines arbitrarily chosen, such a position 
 
 should he assumed tor the arbitrary lines that they .-hall not 
 form a \<v\ acute angle, as iu that case their point of intersec- 
 tion mighl not he determined by the eye with accuracy. For 
 tnple, in erecting a perpendicular to a line at a given point, 
 ami in Like problems, in which points are found by the inter- 
 sections of arcs of circles, it will he usually mosl convenient, 
 
 and best, to take for the radii of the arcs the distance between 
 
 their centres, a.- the angle between the tangents to the arcs at 
 their point of intersection will then he 60°, which is sufficient 
 to give accurately the point where the lines cross. In <■; 
 like I : _--. l". 11. A.rts. 22, 23, the arbitrary lineB a l>, a b\ etc, 
 should he so chosen a- to intersect the horizontals nearly at 
 
SYSTEM OF FORTIFICATION I'KAWlNo. v 29 
 
 . right angles, and so, also, that the resulting lines, by which the 
 points ". "' are determined, shall not intersect in too acute an 
 angle. 
 
 In all Buch cases of determining points, and even where *a 
 point is peeked into the paper by a sharp point, it will be 
 found well to mark the point thus _. by a small circle drawn 
 around it with the lead pencil, as this will present the point 
 with more distinctm 
 
 6th. In determining a portion of a line, by the construction 
 or two arbitrary points, the points should be so chosen that 
 the portion required may fall between them and not beyond 
 them. In PI. 1. Fig 10, for example, it' the required portion 
 of the line of intersection of the planes extended on either 
 side, beyond 0, or «/, or beyond both, the lines </ A, <■<!. etc. 
 should be so chosen as to bring and <>' as far apart, at least, as 
 the length of the required portion of the line which they serve 
 to determine. 
 
 7th. No m€ans of verifying the accuracy of the construc- 
 tion of points, or lines, should be omitted. In PI. 1, Fig. 9 
 for example, other corresponding horizontals should he drawn, 
 
 and if the line of intersection determined by the two points 
 first found is correct, their points of intersection also will fall 
 
 Upon it. In PI, 1, Fiir>. !'. 1". the Scale of declivity of the 
 
 line ..f intersection being determined, the references of the 
 points, where it intersects the scales of declivity of the planes, 
 should l.e the same as the same points on tic if the line 
 
 been accurately determined. A general and minute ven- 
 ation "f all tin parts of the drawing should he made before 
 any portion ..f it i- put in ink. % 
 Mli. a no* unimportant element in the attain- 
 
 t of accuracy in drawing. A few minutias, when attended 
 to, will Bubeerve this end. 
 
 That part of the paper on which the draughtsman is not 
 workii _-. Bnould he kept covered with (dean pap 
 
 the • the board 1 fold over the draw 
 
 which B liould he similarly pp 
 
\ll«'N DRAWING* 
 
 Before oommencing the daily work, the paper should be 
 fully duited, and the and triangles be carefully 
 
 -1 with a/dean dry ra 
 
 few lin. - rtruction as possiblejshould be drawn in 
 
 il ; and only thai part of each which may be strictly nee 
 
 nine the point sought A-. for example, whew a 
 to !"• found by the intersection of two arcs of circl 
 when tin.' position of the point can be approximately judged of 
 by the eya. only a portion of one arc, which will embrace the 
 t, may be drawn, ami the point where the Becond arc would 
 intersect the first be marked without describing tin- arc In 
 PL 1. Fig. 10, instead of drawing the entire lines, a J, c <L etc^ 
 it would De simply necessary to mark the points only where 
 they cut the horizontals, and. in like manner, tlm points <> and 
 ft might be marked without drawing the entire lines. 
 
 No more of any line of the drawing should be made in pen- 
 cil than what is to remain permanently in ink. 
 
 0th. In inking the lines, the following directions will be 
 found useful : 
 
 Efface carefully all pencil lines that are not to be inked, and 
 those parts of the permanent lines which are not to remain, 
 before commencing t<> ink. 
 When right lines arc tangent to curves, put in ink the curve 
 e the right line; draw all arcs, of equal radii at once, one 
 after the other; If several arcs an- to Ik- described from the 
 same centre, it will he well to put ;i tain hit of quill over the 
 point tor the end of the dividers to rest on, to avoid making a 
 hole in the drawing. 
 It' the drawing is not to l^e polored with the brush, all the 
 lines of one color should he put in before co'mmencing on th< 
 of another. 
 
 If one of tin- bounding lines of a surface is to ho made 
 heavier than the others, its breadth should ho taken from the 
 surface they limit and not he added to it; and when the 
 heavy line forms the boundary of two surfaces, its breadth 
 must he taken from the one of greatest declivity. 
 
sV.-'ll.M 01 l COB I IFKATI0N DRAWING. 31 
 
 10th. When the drawing is to be colored, all lines that are 
 not to be black may be pul in firsl with black— making them 
 very faint, so that they may receive theii appropriate colors 
 after the, drawing is otherwise completed. 
 
 No heavy line should be put in until the work with the 
 brash is completed. 
 
 When all the lines are in, the drawing should be thoroughly 
 cleaned with stale bread-crumb; and then have several pit- 
 chers of water dashed over it, the board being placed in an 
 inclined position to allow the water, colored by the ink lines, 
 to escape rapidly, and not to discolor the paper. 
 
 11th. In aging the brush, whether for flat tints, or graded, 
 the requisite depth of tint should be reached by a number of 
 faint tints laid over each other; this is especially necessary in 
 laying tints of blacks, browns and reds. 
 
 To obtain an even flat, or graded tint, on dry paper, is very 
 difficult for a beginner. The best plan for this is, first to wet 
 with a large brush, or clean rag, the surface on which the tint 
 is to be laid, then, with a slightly moist rag, clear the surface 
 of water, and before the paper has time to dry lay on the tint. 
 With this precaution, the heaviest tints of Chinese ink, the 
 most difficult of all to manage OH dry paper, can be neatly laid 
 down. 
 
 12th. The lettering and numbering of a drawing should be 
 in ordinary printed: character; this is particularly requisite in 
 the numbering, to avoid misapprehensions which might arise 
 from individual pecularities in writing numb 
 
 As has been already remarked, references are written in 
 
 black, within brackets, which, when practicable, embrace the 
 .t referred to. When not practicable, a small dotted line 
 may lead from the point to the n »,50); 
 
 but to distinguish r< P from other numbers the designa- 
 
 tion of the unit is omitted. 
 
 All horizontal distances between point- .are written upon a 
 
 dotted line drawn betwi en the point-, with an arrow head at 
 
 partial di.-tanc a in a right lin< 
 
SYSTEM 01 1 "Kill 1< AXIOM DB \w IXC 
 
 marked, it will lie abo well to mark the total distance — the 
 latter may be written above or beneath tin- former, El. 9. 
 
 In writing horizontal distances, the usual designation of the 
 unit i.- always written thus; y for yards, ' for feet, etc. All 
 the numbers musl be expressed in tin- same unit; the frac- 
 tional parts being in decimals. 
 
 References and horizontal distances cannot he too much 
 
 multiplied, in order t" avoid misapprehensions, and the results 
 
 rrora of construction, is well a- to save ^ie time that 
 
 would he taken in applying dividers to the drawing to find, 
 
 from the scale affixed to it. the dimensions of any part. 
 
 A scale very accurately constructed should he affixed to the 
 drawing before it is cut from the hoard ; so that the shrinkage 
 of the paper, which is about L-500, may affect all the parts 
 equally, and the scale thus In- made to correspond to the real 
 lengths of the lines on the drawing. The scale should he di- 
 vided according to the decimal BVBtem, as being most con- 
 venient for counting off. 
 
 The lir.it division of the scale should furnish the units, and 
 also their decimal parts, if the scale hears that proportion to 
 the true dimension,- of the object represented which will ad- 
 mit of these divisions. This first division is numbered from 
 right to left, PI. L\ Fig. !», the zero point being on the right, 
 the 10 point on the left ; the succeeding divisions, to 50 inclii- 
 ould each he equal to the first division, containing ten 
 uint.- each. The remaining divisions may contain fifty units 
 each. It Mill he >eeii that any number of tens, units, or frac- 
 tional part.- of a unit, can thus he readily taken off from the 
 scale by the dwiders. The scale should he long enough to 
 'he dimensions of the longest line on the drawing. 
 
 The proportion which the scale hears to the true dimensions 
 of the object should he written above the scale ; thus, seals one 
 'in.}, /.- t. n yards, <>,■ L-360. And the designation of the unit 
 of the drawing should he annexed to the last division on the 
 
 . S, a.- yds. for jBlda t J't, for feet, etc. 
 
PERMANENT FORTIFICATION. 
 
 PRELIMINARY CONSIDERATIONS. 
 
 41. ..The term j» rmam nt fortification is applied to those de- 
 fences which, constructed of materials of a durable nature, and 
 designed for permanent occupancy by troops, receive such a 
 decree of strength that an enemy will be forced to the opera- 
 tions either of a siege or a blockade to gain possession of them. 
 
 42. ..The object of such defences is to secure the permanent 
 military possession of those points, either on the frontiers or in 
 the interior of a State, which must, at all times, have a well- 
 defined bearing on the operations of a defensive or an offen- 
 sive war. 
 
 r:...l'<>r the attainment of this object, the following general 
 condition.- should be fulfilled in the arrangement of such de- 
 fence;-: Let, they should be of sufficient strength to resist with 
 .-access all the ordinary means resorted to by an assailant in 
 an open assault; 2d, be provided with suitable shelters to pro- 
 tect thy troops, the armament, and the magaQnea of provisions 
 
 Bad munitions of war required for their den : n-t the 
 
 active measures of the assailant, of e-. . : ::d. 
 
 be so planned that every point exterior to the thin 
 
 cannon range .-hall be thoroughly swept by their fire; 4th, 
 
 have secure and easy m< . ominunication for the move- 
 
 6 
 
:m \ni:nt works. 
 
 incuts of the troops, both within the defences ami to the e\- 
 5th, and finally, be provided with all such accessory 
 
 naive in. the natural features of the position itself 
 
 may afford, to enable the garrison to dispute with energy the 
 occupancy by the assailant, of every point both within and 
 
 rior t(» the defenc 
 Tin' defensive branch of the military engineer's art consists 
 in a knowledge «>t the means which are employed to fulfil the 
 above conditions, and of their suitable adaptation to the 
 natural features of the positions ho may be called upon to 
 fortify. 
 
 IWHXEXT ELEMEXTS OF PER1IAXEXT WORKS, 
 
 (iKNKRAL PROFILE. 
 
 •I I. ..The first condition laid down for permanent defences, 
 security from open assault, supposes a Btrength of profile 
 greatly superior to that which is given to temporary works. 
 
 l.'....'1'lic usual and most simple form of profile for perma* 
 iM-nt works consist of a rampwrt^ a parapet, and a ditch, the 
 ioarp and oounterscarp of which are faced with steep malls of 
 ttone, or brick) and exterior to which a glacis is usually thrown 
 up. When the ditch contains at all times a depth of water 
 sufficient to prevent it> being forded, the scarp and counter* 
 scarp may be simply Blopes of earth like those of field works; 
 the water, with ordinary vigilance on the part of the de- 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 35 
 
 fence, will give security from surprise, and all the other ordi- 
 nary means of an open assault. 
 
 46. ..The rampart, A, PI. 3, Figs. 4, 6, is an earthen mound, 
 raised above the natural level of the ground, ami upon which 
 the parapet, B, is placed. The rampart thus serves to give 
 the troope and armament, which are placed on top of it and 
 behind the parapet, a commanding view over the ground to 
 lif guarded by the lire of the defences; whilst, at the same 
 time, it increases the obstacle to an open assault, by the addi- 
 tional height it gives to the scarp. 
 
 47.. .The top surface of the rampart, h c, in rear of the para- 
 pefc, termed the terreplein, affords the troops and armament a 
 convenient position for circulation from point to point, where 
 they are sheltered from the direct views of the assailant's fire. 
 
 4 s . ..The rampart is usually terminated on the interior, a b. 
 by allowing the earth to assume either its natural slope or one 
 somewhat less steep, and which is termed the rampartrtlope. 
 In cases where this slope would take up too much of die ground 
 within the defences it is replaced by* wall, termed theixwadt 
 wall) which rises from the level of the interior ground, termed 
 the parad* . to the interior line of the A rrepli >n. 
 
 id.. .Inclined planes of earth, termed ra/nj/s, lead from the 
 parade to the terreplein, being placed against the rampart-slope 
 or the parade walL The ramp.- arc. in some cases, terminated, 
 inwardly, with the same slope as that of the rampart ; in oth- 
 
 . this slope is replaced by a wall, which rises to she top ,-ur- 
 of the ram]-, or a little above it. 
 
 .'."...Tin' parapet, serving the same pm permanent 
 
 D field works, receive ne general form as in the lat- 
 
 ter, [nsome cases, the exterior slope, PL •'•. V j. 12, 
 placed by a wall, which, resting on the top of the scarp wall, 
 
 level of the snpi rior .-lope. The exterior sloi 
 the parapet usually rises from the top of the scarp wall, leai 
 I narrow berm betwi i □ it and the scarp or the wall. 
 
 thrown so far to the n ar of I I ' 
 
 8, 1 _- 9, 10, ai >m for a communication, 
 
OOMl'oNl M 1 !.l M HUMAN! NT Works. 
 
 i front of tin- parapet, in which tlic troops can circulate 
 undi r from lire being masked either by an earthen 
 
 parapet, or by a wall. I >. Tliis covered communication, G 7 , is 
 termed an exterior corridor, or cJiertyvrirde-rondee. 
 
 51...The scarp wall, C, PI. 3, Figs. 4, 6, retains the earth of 
 tin- rampart and parapet, and forme, by its height ami steep* 
 . tli.' chid' obstacle to an open assault* The top stone of 
 the wall. l\ termed tin- cotdon, or coping, projects beyond its 
 face, and, serving as a la/rmeir, or drip, protects it from the 
 effects of the rain-water which rims from the parapet upon the 
 coping. 
 
 52.. .The line in which the face of the scarp wall, prolonged, 
 would intersect the coping, is termed the magistral. This is a 
 very important line in drawing the plans of permanent works, 
 serving as the directing line to fix (both upon the drawing ami 
 upon tlu' ground in setting out the work). the dimensions and 
 relative positions of all the bounding lines of the parapet and 
 other parts. 
 
 53. ..Th<- counterscarp wall, er, renders the ditch of more 
 difficult access from without than an earthen slope would: and 
 when of sufficient height and steepness, it tonus a very serious 
 obstacle to an open assault. It receives the same general forms 
 as the scarp wall. 
 
 ..I. ..The glacis, F, is of the same form, and serves the same 
 purposes as in field works; but, besides these, it is indispensa- 
 ble sa a mask for the scarp wall, covering it from distant 
 batteries, in cases where it rises above the level of the coun- 
 terscarp, ami thus forcing the assailant to construct his batteries 
 along the cresl of tin- glacis, to obtain a position from which 
 the scarp wall ran be breached. When the glacis serves only 
 mask, and to bring the assailant, as he rushes forward in 
 an open assault, better under fire, it is brought in so as to rest 
 on top of the counterscarp wall. But in cases where a covered 
 communication is needed beyond the ditch, the glacis is thrown 
 outward far enough to leave the requisite space between it 
 and the counterscarp. This sheltered position is termed the 
 
 4 
 
COMPONENT ELEMENTS OE PERMANENT WORKS. ."-7 
 
 covered-way. It servos both for the circulation of the troops, 
 from point to point, and as a defensive position ; the pert of the 
 glacis facing the covered-way being arranged, for this latter 
 purpose, like an ordinary earthen parapet. 
 
 55. ..Mounds of earth which are formed solely with a view to 
 mask a scarp Avail from fire are termed fa ■• covt rs. They may 
 be either in the form of a glacis, or receive, on each sid<\ the 
 slope which the earth would naturally take, sufficient height 
 and thickness being given to them to subserve the object to be 
 attained. 
 
 56. ..Among the modifications of the usual profile is the one 
 represented in PI. 3, Fig. 11, where the scarp wall, rising Only 
 t<> the level of the site, is surmounted by a parapet wall, I), 
 which covers a ohemi^rde-rondes, C. This parr of the work is 
 termed &faus8i -/</•■//< . By dividing the entire height of scarp 
 wall into two parts, thus rendering each more accessible to an 
 open assault, and by exposing the troops in it to injury from 
 the splinters from the scarp wall behind them, caused by the 
 tin- of the a.-sailant, the fausse-braie has fallen into disuse. 
 
 *>7...The introduction, within the last thirty years, of the 
 barbette gun-carriage, now in general use for permanent works, 
 has led to a modification in the form of the profile, with a view 
 of better adapting it to the new carriage. This change is 
 shown in PI. 3, Fig. 4^ and consists, mainly, in raising the level, 
 (1 r, <it' tlir terreplein fifteen inches, placing it thus at six feet 
 nine inches below the interior crest, for a distance of twenty 
 feel back from this crest, and connecting it by a slope, •■>/. of 
 45° with the level bel<>w; the parapet receives an interior slope, 
 // y. of 1.*)°, which falls upon a banquette, /\/, for infantry, the 
 tread of which is two feet, and is placed at four feet six inc 
 below, //. the interior crest. The banquette-slop< . two 
 
 to one perpendicular, and tails upon the raised portion, 
 <1 < . of the terreplein. When it is necessary to place guns in 
 battery along any portion of a parapet having this form of 
 profile, the interior slope U cut down, nearly perpendicularly, 
 t<» the level of the raisi d portion of the terreplein, and fit 
 
 ™» 
 
 & 
 
i i ! HEN r8 OF l'KKMANl NT W0BX8, 
 
 with fascines ; the earth between tibia raised portion and the 
 new interior Blope being removed, a Level and solid bed is 
 the carriages. The surplus earth that lias to 
 l, r removed by this operation can be used for ordinary 
 traverses, and for increasing the height of the merlons when 
 tin- parapet ia pierced for embrasures. 
 
 58...The dimensions and forms of the different parts of the 
 profile are so established as to afford security against an open 
 .It ; sufficient command of the parapet over the exterior 
 ground to BWeep it effectually by its fire; cover from the fire 
 ot tin- assailant ; and ample room with suitable arrangements 
 for the delivery of the fire of the assailed. 
 
 .'.:<..>, \i;r. A scarp wall, 30 feet high, is usually admitted 
 a- a sufficient protection in dry ditches against an escalade. 
 
 This rule, drawn from the experience of sieges, and the 
 opinions of the most eminent engineers, seems a safe one; 
 since to scale a wall of this height would require ladders of 
 sufficient length to enable the men who ascend to step from 
 the ladder, when planted securely against the wall, ou the 
 Doping, and of sufficient strength to hear the weight of six or 
 eight men mounting together. 
 
 To carry forward ladders of the dimensions requisite for this 
 purpose and place them ill position, with that promptitude 
 upon which the success of an open assault must mainly 
 depend, Mould, of itself, be an operation of no slight difficulty; 
 but, when it is considered that the assailants are exposed to the 
 lire of the defences before reaching the ditch, which from its 
 width and depth alone renders it a serious obstacle, and that 
 after they have entered the ditch they are still under the fire 
 by which it is flanked, it is difficult to imagine how the at- 
 tempt could succeed if the assailed offer even an ordinary 
 degree of resistance. 
 
 60...For wet ditches filled to the depth of six feet, and thus 
 secured from being passed by fording, a height of scarp of 24 
 feet is < sidered sufficient security from an open assault. 
 
 til. ..Solid .-ear]) walls, with ordinary counterforts, I), receive 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 39 
 
 the thickness requisite to sustain the pressure of the earth rest- 
 ing against their hack. The batter given them on their face 
 varies in different services. In Vauhan's profiles the hatter is 
 5-1, or five perpendicular to one hase. In Oormontaingne's it 
 is 6-1. But from the effects of time, as observed in the works 
 built by these engineers, the slopes of their walls are too great. 
 In the French service, a slope of 20-1 is now usually given. 
 In the Austrian, 12-1 ; and in our own, from 24-1 to 48-1. In 
 this diversity of practice it is only necessary to remark, that 
 the steeper walls are better protected from the effects of the 
 weather, and tin's is a very important consideration in struc- 
 tures demanding great durability. 
 
 62. ..Parapet. The essential properties of the parapet are 
 to afford cover, and facilities for sweeping the ground exterior 
 to it by the artillery and musketry. Its form and dimensions 
 arc therefore, so adjusted as to fulfil these requirements. 
 
 63. ..For the service of the artillery, barbettes are constructed 
 behind the parapet, and suitably arranged either for guns 
 mounted on the ordinary traveling carriages, or upon the 
 traversing carriages, which, within some years back, have 
 been introduced for the armament of land and sea-coast fronts; 
 and embrasures are pierced in the parapet for like purposes. 
 
 84... As the sole of the embrasure is usually not more than 
 three feel below the superior slope, and generally parallel to 
 it, care must be taken so to adjust its position with respect to 
 the coping of the scarp wall that, when the guns are fired 
 under the same depression as the superior dope, the balls 
 shall clear the edge of the Coping sufficiently to prevent its 
 being injured by negligent firing. This requirement will 
 e to determine the least height of the parapet above the 
 coping, and which may be done by either of the following 
 methods. 
 
 66. ..Supposing the parapet to be formed of earth of the or- 
 dinary character. PI. 4, Fig. 14, in which the natural slop 
 45°, or 1-1 : the superioi slope, which is the san i1 of 
 
 the embrasure sole, is !-«'•, the one usually adopted as the 
 
PI KMAN; N 1 WORKS. 
 
 • for the parapets of permanent work-: the thicknee 
 tin- parapet i v feet, the least given to it to resist the heavi 
 calibre thus far employed} and that a berm of two feet 
 allowed on the top of the Bcarp wall, between the edge of the 
 
 ing and the foot of the exterior slope: let a horizontal line, 
 . be first drawn at the level of the coping) and, from its ex- 
 terior edge, ". a second line, </ c, making an angle of 1-6 with 
 a //,- this hist line will be the direction of a shot tired under 
 tin' depression of 1-6, which would, just graze the edge of the 
 coping, and may be assumed as the lowest position that the 
 of an embrasure can receive; a line, therefore, drawn 
 
 .lid to it c and ."- feet above it. will be the lowest position 
 also of the superior slope. It' a line is now drawn through a, 
 the interior edge <>f the berm and the fodt "t" the exterior slope; 
 making an angle of J-l with a b, it will be the direction 6f the 
 exterior slope; and the point m, where it cuts the direction of 
 the superior Blope, will he the exterior creSt of the para] iet . 
 
 Setting off along the horizontal line through m the thickness 
 
 of the parapet, or i x feet, and erecting a vertical at the point 
 
 thus determined, the point //, where this vertical cuts the 
 
 superior Blope, will give the position of the interior exeat, », 
 
 and, consequently) will determine its vertical height above the 
 
 ing. 
 
 66. .. The. following simple calculation will, in like manner, 
 
 give the same result. Denote by x the base < </—</ m of the 
 
 rior Blope. As the berm */ < =2 feet, the thickness of the 
 
 parapet d b 1 v fed ; the distance '' U—a e+e (/+</ l>='2'+x+ 
 
 l&'=x + '2"' : hut since the line <i <■ makes an angle of l-<! with 
 
 </ />. the point .-. where it cuts the vertical through '/, will 
 
 make b 0=1-0 a J, and, as from the position of the superior 
 
 slope ami the thickness, 1 N feet, given to the parapet, the 
 
 point // is three feet above the points /// and <•. it follows that 
 
 </ /// = ,r. Therefore, from the two preceding equations 
 
 there obtains .<•— l-t; (x+Qtf); hence x=± feet. Prom this 
 value of ,;, the height b oof /<, ahovs the point a, is 7 feet ; 
 which, under the assumed conditions, is the least height of the 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 41 
 
 interior crest above the coping in which a ball, passing in the 
 same line as the sole of the embrasure, would just touch the 
 exterior edge "f the coping. In order to secure the coping 
 from damage, the interior crest is placed 8 !'<•<■! above it. 
 
 It should he observed thai flic result here arrived at, being 
 dependent on the assumed data, will vary by changing the 
 elements of the problem. 
 
 ST.. .The height of s feet thus determined, as the least which 
 the parapet should receive above the magistral, is advanta* 
 geous both as to economy ami for the defence, and, therefore, 
 should not be exceeded except fur good reasons. This will 
 be apparent, when it is considered that the pressure on the 
 scarp wall, from the weight of the parapet, increases with the 
 height of the latter, and that the wall must he made stroo 
 in proportion ; and. although an increased height of parapet, 
 by increasing the obstacle to an escalade, is in favor of the 
 defence, still, when it much exceed:, g feet, the assailant, on 
 reaching the top of the wall, will find shelter from the fire of 
 the parapet, which will pass above his head, and he will be 
 better enabled to reach the top of the parapet than when 
 partly exposed to this tire, as he will be in low parapets. 
 
 •'.v.. The inclination of l-»i has been generally adopted as the 
 •e.-t inclination of the superior slope, both on account of 
 the greatest depression that guns can be fired under without 
 straining too much tin,' carriages, and to avoid making the por- 
 tion of the parapet near the interior crest BO weak that itcould 
 be readily destroyed, and the troops and materiel exposed to 
 view. When. \ < r the held of tin- will admit of it, it will 
 prove advantageous, under these two points of view, to gii 
 smaller inclination to the superior slope. In ca-es where it is 
 
 able to reach Borne point, by the tire requiring a 
 slope than I-'!, it may be done without inconveni the 
 
 parapet is not likely to f. d to a heavy fir ible 
 
 inclination being also given t<» the gun-platform. 
 
 terior slop-, for the i in disi 
 
 the parapets of field works, should not be land fin 
 
 •; 
 
■!:_' ELEMENTS OF PERMANENT WOBXfl. 
 
 than the natural Blope of the earth of which the parapet is 
 formed. In I works, where the parapet i> hiirh, and 
 
 be reached, within cannon range, only by elevating the 
 guns of tin- ships, the exterior slops may be replaced by a 
 vertical revetement of stone, or one oi Bods with but a slight 
 inclination, as, from the direption of the lire, this facing, even 
 it' partially destroyed, will not cause Buch weakness in the 
 parapet as to expose the troops. By using a facing of this 
 kind, the parapet will occupy Less room and Leave more interior 
 . which, in small works, is often desirable. 
 
 7". ..A.- a berm of two feet affords a tolerable landing to the 
 hint in an escalade, it would he hitter to make it 
 particularly on fronts open to Bach an assault. Tin- usual 
 berm may It given when the work is constructed, and he after- 
 ward Lessened by increasing the thickness of the parapet when 
 tin- work is to he placed in a defensive attitude. 
 
 71. ..The thickness of the parapets of ordinary earth seldom 
 exceed 30 feet. This is the dimension usually given in Euro- 
 pean constructions of important works liable to a long expo- 
 sure- to lire, and has luen found, by experience, to afford good 
 i- against a well-nourished and protracted tire of the 
 heaviest calibre thus far \\>vA. In our service, a thickness 
 l v feet has been more usually given. For less important 
 works, and particularly when- parapets arc not likely to he 
 systematically battered, the thickness may be safely reduced 
 to L2 or IT) l'( « t. 
 
 72.. .In the form of profile given in PL 3, Fig. 4, the portion 
 of the terreplein on which the guns rest in battery is placed 
 it a level below the interior crest, to. admit the guns being 
 tired over the parapet ; and this difference of level is sufficient 
 t.. give good cover along the parapet to the men serving the 
 guns. The portion, b <\ <<\' the terrepleiu to the rear of this 
 a communication along the line of fortification, and, 
 being further hack, should he Bomewhat Lower, to afford good 
 
 or fr shot just passing over the interior crest. It is osu 
 
 ally placed at a level of 8 feet below the interior crest ; aslope 
 
 ** 
 
 
COMPONENT ELEMENTS OF PERMANENT Works. 43 
 
 of one foot inward being given to it, estimating it from the line of 
 the interior crest to the exterior edge of the terreplein; to free 
 it rapidly from the rain-water. This level, however, may !>c 
 lowered if the irregularity of the site requires it, from the 
 command the exterior ground may have over the work. In 
 all cases it will be rather a question of economy, to be decided 
 by the amount of excavation and embankment. As the space 
 in question serves chiefly the purposes of a communication, it 
 may be reduced, through motives of economy, to a width 
 which will be sufficient for the gun-carriages arid other ve- 
 hicles employed in the defence to pass each other. For this 
 purpose the entire width of the terreplein, estimating it be- 
 tween the verticals through the interior crest of the parapet 
 and the crest of the rampart-slope, has usually received 42 
 feet in enceintes of importance where a circulation of the kind 
 just mentioned is to be provided for. In other cases it. may 
 be reduced to 24, or even 20 feet. It should be remarked, 
 however, that, as a wide terreplein facilitates the disposition Of 
 troops for an active defence of the breach, it should not he too 
 much reduced along those portions of the enceinte exposed to 
 
 he opened. 
 
 ..The rampart toward the parade usually receives a slope. 
 greater than that which the earth would naturally assume 
 where the interior space admits of it. This will offer the means 
 
 of forming narrow foot-paths along this slope leading from the 
 parade to the terreplein at convenient points, and prevent the 
 
 slope from being injured, which it is apt to he hy the men 
 
 ping such Bhort cuts for thee Where the int. 
 
 Bpace would he too much circum.-crihed. this slope may b< 
 
 placed by a parade wall. 
 
 71. ..The banquette-tread and the interior shown in 
 
 PL i I. will answer sufficiently well for ordinary pur- 
 
 poses; hut where a warm tire in two ranks is to be sustained, 
 the interior slope should be trimmed down to the 
 
 ■■ Inch will, at tie 
 
 banquette-tread so ai two rank.-.. It would he well. 
 
 C"* 
 
 ■l^fu 
 
 V 
 
11 COMPONENT ELEMENTS OT PEEMANENT works. 
 
 also, in making these changes for an active defence, to raise the 
 banquette-tread bo within a tevelof4j feet of the interior en 
 for tin' greater convenience of short men in delivering their 
 fire. 
 
 7. ...V d <'t' the parapet over the site has a very 
 
 important bearing in the defence of permanent works, as the 
 ilanf meets with the more difficulty, in running forward 
 his trenches, as the fire of the defences becomes more plung- 
 ing. Motives of economy, however, require the command to 
 be restricted within quite narrow limits. When the work con- 
 sists of a simple enceinte, enveloped by a covered-way, the 
 command may be reduced to 16 feet, allowing a command of 
 s feet to the interior crest of the glacis over the site, and a 
 height of 8 feel to the interior crest above the coping, which, 
 with the rest of the scarp wall, to be masked by the glacis, 
 musl not rise above the level of its' interior crest. Where 
 there are other outworks besides the covered-way in defensive 
 relations with the enceinte, the latter' cannot receive a com- 
 mand over the site of less that about 20 feet, in order to give 
 it a suitable command over the whole of the outworks. 
 
 7<i...('or.\'ri:i:scAi;i> Wall. A revetted counterscarp is re- 
 garded as adding to the difficulty of descending into the ditch, 
 and as offering greater security against an open assault. For 
 this purpose the wall should not be less than 12 or 15 feet in 
 height, to oiler a serious impediment; in any case where mo- 
 tives of economy do not imperiously demand it, the countcr- 
 BCarp wall of the enceinte should be from 18 to 21 feet in 
 height. This height will not only give great security to the 
 ditch, but, as will be seen in the description of the siege works 
 of tlu' assailant, it will delay, considerably, his progress, as 
 the gallery by which he must generally reach the bottom of 
 the ditch from the level of the covered-way terreplein, is one 
 of the slowest and most laborious of his operations. 
 
 7T...I)ii( ii. The width and depth of the enceinte ditch de- 
 pends mainly upon the amount of embankment required for 
 the enceinte and the glacis, and, therefore, will result from the 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. \~> 
 
 calculation for equalizing the excavation and embankment 
 which these demand. A deep and narrow ditch offers the ad s 
 vantage of presenting more difficulty to the assailant in reaching 
 the bottom of it ; and, from the position he is obliged to take up 
 for his breach batteries to open the scarp wall, his fire cannot 
 Bee the wall so near its foot as in a wide ditch, and the breach, 
 therefore, may, from this cause, be less practicable. A wide 
 ditch, on the other hand, requires more lahor to construct the 
 trench across it, by which the assailant can reach the foot of 
 the breach undercover. This is a consideration of some im- 
 portance in wet ditches, where the assailant is obliged to con- 
 struct a dike, upon which the parapet of his cover is placed. 
 In the practice of engineers the enceinte ditch has received a 
 width of from $0 u> 80 yards when dry, and from 30 to 45 
 yards when wet. These dimensions may he reduced to within 
 10 or L2 yards, where the embankments are not great, and cir- 
 cumstances an' unfavorable to an attempt at escalade. 
 
 7*. ..The bottom of the ditch usually receives a Blight slope 
 iron i the foot of the scarp and counterscarp to its centre, 
 where a small drain, termed a OUnetfa, is dug to receive the 
 surface water and keep the ditch dry. In BOtne cases, from 
 motives of economy, the difference of level hetween the 
 cunette and the foot of the counterscarp walls is increased) 
 thus giving a l< bs height of wall. This practice, however, can 
 only be followed where the foundations of the wall will be 
 secure from the soil of the bottom of the ditch being of such a 
 nature as not to yield from the effects of the weather upon it. 
 
 79...Geneeal Remarks. The rule- here given with respect 
 to the form and dim of the general profile of till 
 
 ceinM are founded upon reasons growing out of the nature of 
 the question, and as -uch have Berved a> guides to engii 
 in the practice of their profession. A.a they have stood, he- 
 side.-, the test of long experience, i1 follow them, 
 whilst at the same time the engineer should not heeitat 
 vary from them when satisfied, afl ul examination, that 
 the. fore him requires it. Fortification, it mutt 
 
46 OOMPOH PERMANENT WORKS. 
 
 membered, is like all other arts. It has its canons which are 
 founded upon the nature of the question, and its rules of prac- 
 tice based upon these and upon experience. As the latter pre- 
 sents i" the engineer new tacts, his practice must be made to 
 conform to them, hut the general principles oi his art must 
 ever remain the Bame and be his invariable guide. 
 
 OPEN DEFENCES. 
 
 80...Bj this term is understood the dispositions made for the 
 action of the troops and armament which are covered from the 
 misajles of the assailed by the parapet alone. 
 
 Bl...To this class belongs the arrangement of the parapet 
 
 which has already been described; simple looj>-lu>lil walls for 
 musketry, used as enclosures of gorges, etc.; e.ctrri<>r corridors 
 which are covered either by a wall or an earthen parapet; 
 and "barbettes and embrasures for artillery. 
 
 82...LoOP-BOLED Walls. Walls of this class when used as 
 the enclosures of the gorges of lunettes or other isolated works, 
 placed in advance of the enceinte, but within the reach of its 
 artillery fire, should be high enough to secure the work from 
 an open assault, and sufficiently thick to resist the occasional 
 shot which may reach them over the parapet by which they 
 are covered. For these purposes the height, PL 4', Fig. 24, 
 should be from 12 to 15 feet, and the thickness from 4 to 5 
 feet. The loop-holes arc not placed nearer to each other than 
 from 3 to 4 feet, estimated between their axes. They should 
 be at least 6 feet above the exterior foot of the wall, and 4J 
 feel above the ground or banquette within. The loop-holes 
 are usually placed at regular intervals along the line ef the 
 Wall; or only opposite that portion of the exterior ground 
 upon which a fire is to be brought to bear. 
 
 83. ..The form and dimensions of the loop-hole will depend 
 upon the thickness of the wall and the field of view, both ver- 
 tically and horizontally, which is to be covered by its fire. 
 The plan is either trapezoidal, PI. 4, Figs. 17, 20, widening 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 47 
 
 from the front of the wall inward, or else it widens from the 
 centre each way to the front and back; or, as is the more 
 usual form in our works, the interior portion from the centre 
 widens inward, whilst the exterior part is rectangular in plan. 
 The first form is best adapted to walls not more than 2$ feet 
 thick; the others to heavier walls; the object being to lessen, 
 as far as practicable, the weakness which loop-holes necessarily 
 cause to the wall; this defect increasing as the exterior or 
 interior opening is greater. 
 
 84.. .For thin walls, where the plan of the loop-hole is tra- 
 pezoidal, the width of the exterior opening may be from 2 to 
 4 inches, and that of the interior from 15 to* 18 inches. These 
 dimensions, however, may vary according to the field of fire 
 to be brought within the range of the loop-hole, the more or 
 less cover to be given to the troops, and the strength of the 
 masonry of which the wall is formed. The vertical dimensions 
 of the loop-hole, both on the interior and the exterior, will 
 depend upon the field of fire to be embraced in this last direc- 
 tion, and they will be regulated accordingh T ; the slope of the 
 top and sole of the loop-hole receiving a suitable slope or 
 direction for this purpose. 
 
 The foregoing details can only be well determined upon 
 from the special object to which the loop-holed defences are to 
 be applied. Care only is to be taken that, in attempting to 
 give cover to the troops, their ijeld of view be not too restrict- 
 ed, by too narrow an opening for the use of the iire-arms. 
 
 85...Wnere the throal or narrowest part of the loop-hole is 
 within the wall, the exterior opening leaves a wider mark for 
 
 the missiles of the assailed' and when the sides of the loop- 
 hole gradually widen outward a .-hot striking .me of them may 
 glance inward and do injury. To prevent this accident 'lie 
 sides and sometimes the Bole are made in offsets. This, how- 
 ever. [| not so convenient a mode of constructing the loop- 
 hole, nor one so efficient in arresting the shot which do not 
 directly attain the throat, a.- the one in PI. A. big. 1. which is 
 the plan of one, taken from our works, pierced in a wall o" 
 
•poMAT ri. l M PERMANENT WOBKf. 
 
 feet thick. The plan of the exterior portion, a, is rectan- 
 gular, the exterior width 2 feet; the throat is at the centre of 
 
 tlie wall, ami 6* wide; the interior portion, $, is trapezoidal, 
 and _ feet wide <>n the interim-. 
 
 ..In open exterior corridors the loops are covered in front, 
 either by an earthen parapet, which is usually only musket- 
 proof, the scarp wall being run up to the superior Blope, or 
 the Bcarp wall serves as the cover, in which case it is 
 pierced either throughout its Length or at suitable points with 
 loop-holes. The floor of the corridor, C\ PI. 4-, Fig. 27, serves 
 as a banquette-tread for the loop-holes, and is, therefore, 
 placed with reference to the direction of the fire from the Loop* 
 holes. The height at which the scarp wall rises above the 
 floor of the corridor will depend upon the level of the floor 
 and that of the bottom of the ditch; this height, however, 
 Bhonld not be less than 6£ feet, to afford sufficient cover to the 
 troops. 
 
 87.. .Scarp walls of this arrangement are termed semi-de- 
 tacked, to distinguish them from the ordinary retaining scarp 
 walls and those in which the wall is entirely separated from 
 the rampart, serving as a simple enclosure to it to prevent an 
 escalade, 
 
 88.. .The preceding Figure is given as an example of a semi-de- 
 tached M-arp, A, an earthen counterscarp, and covered-way, 
 D ; being a section of an outwork of one of our sea-coast 
 forts. 
 
 Mi... I! ak]5Ette Batteries. For guns mounted on the ordi- 
 nary held and siege carriages, the barbettes are constructed 
 in the same manner and with the same dimensions as in field 
 works. The arrangement of the ramps and slopes being deter- 
 mined by the position in which the barbette is placed, and its 
 relative position with respect to the terreplein and parapet. 
 
 0O...FoT the heavy guns used in forts, both for sea and land 
 fronts, a solid foundation of stone is laid to receive the pintle 
 and rail, upon which the chassis of the gun is made to tra- 
 verse* This foundation consists of a heavy block, set firmly in 
 
COMPONENT ELEMENTS OF PERMANENT WORKS* li' 
 
 abed of beton,' to which the pintle, placed at the centre of 
 motion, is solidly attached; and of stone blocks set in like 
 manner, to which arc firmly attached the iron rails, which 
 cither form a segment of a circle, as in PL 7, Figs. 54-, 55, or a 
 complete circle^ as in iFigs. 56, 57, 58, upon which the tra- 
 verse-wheels ran. 
 
 91. ..In order to afford the gun a wide traverse, a recess is 
 made in the parapet in front of the carriage, of sufficient 
 dimensions to allow the manoeuvres of the chassis and top car- 
 riage without obstruction; for this purpose it has received a 
 depth of "2 feet, its front 5 feet; its two sides having a slant of 
 .'in inches base to 24 indies perpendicular, The recess, and 
 Usually the entire length of the battery front, is faced with a 
 breast-height wall that only rises to within 18 inches of the 
 top of the parapet; its thickness being 2 feet. The Figures 
 referred to give the plan, sections and elevation of the barbette 
 arrangements in question adopted in our service. 
 
 92... Embrasure Batteries. The embrasures cut in the para- 
 pets for -mis on field and siege carriages, differ in no essential 
 point from those for field works. It is well, however, to ob- 
 serve, as the parapet is weakened by receiving embrasures, the 
 Bplay given to them should, in all cases, be carefullv regulated 
 by the held of fire it is desirable to command, so as to Leave 
 "as large a mass of merlon between each, as practicable, to 
 ailant's fire. 
 
 93... For guns mounted on sea-coast carriages the embrasures 
 are very shallow, merely covering the gun from lateral view. 
 PL A, Fig. 2 is a profile of the enceinte through the axis of 
 an embrasure of r< cent French works, showing the manner in 
 which the profile is modified and revetted for the servi© 
 the pie© 
 
 '.tb..M \< nir.'iu-. For the purpose of attaining, by mus- 
 ketry, the foot of a scarp wall without flank defences, resort 
 must be had to S machiconlated arrangement at the top of the 
 Bcarp. 
 
 nal mode adopted for this purpose, PL v . 1 
 
 7 
 
.".'i :.""MM i i.i mi n is OF PERMANENT WORKS. 
 
 »;;. | form a parapet wail, which rests upon a wlid 
 
 horizontal band of Btone, mar the top of the scarp, which is 
 supported on corbels, or projecting blocks, firmly built into 
 the wall. The back of the parapet wall is placed a few inches 
 in advance of the scarp, leaving room for die slanting loop- 
 holea pierced in the horizontal band through which the lire is 
 to be delivered on the toot of the scarp. The top of the para- 
 pet wall is also arranged to admit of firing on more distant 
 points. 
 
 !•<;.. .In the example given, which is from an Austrian 
 authority, Fig. 07 is a front elevation, and Fig. OS a section 
 through a loop-hole. 
 
 Figs. *!.'), fit!, are a front elevation, and section through a 
 Loop-hole, from the same authority. This is a semi-detached 
 scarp wall, the top portion of which is arranged on the back 
 with loop-holed recesses; the lower portion having very in- 
 clined arched recesses in front, with slanting loop-holes to tire 
 on the foot of the scar]) from the upper recesses. 
 
 97. ..Whore, from the irregularity of the site, tlfe ordinary 
 machicoulis cannot be made efficient, resort may he had to 
 small polygonal chandlers of stone, open at top, and having 
 the sides and bottom pierced with loop-holes and machicoulis. 
 These constructions may he made just of sufficient size to hold 
 a .-ingle sentinel. They are placed at the angles of the works, 
 where they will not be exposed to artillery, and are supported 
 on a corbel work projecting from the top of the scarp wall. 
 
 COVERED DEFENCES. 
 
 98...Dktacui:!> Scarp Walls. When the scarp walls are 
 entirely detached, leaving an open corridor between them and 
 the rampart, they are pierced with one or two tiers of loop- 
 holes from which a fire can be brought from the ditch and 
 upon the terreplein of the covered-way, or any work in front 
 of the enceinte. 
 
 99.. .To give cover to the men at the loop-holes, arched re- 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 51 
 
 cesses, PI. 4, Figs. 25, 20, are made in the thickness of wall, 
 ox else short counterforts arc built hack from the Avail which 
 serve as the piers of covering arches. The width of the re- 
 •s should admit of three or four loop-holes at the usual 
 distance apart; their height and depth be sufficient to give 
 the men shelter from vertical lire, and allow them to handle 
 their arms with convenience. 
 
 100. ..The two Figures above are sections of this description 
 of scarp wall taken through the crowns of the arches, as shown 
 in an Austrian work. A, is a section of the wall ; B and D y 
 elevations of the sides of the recess; C, an elevation and sec- 
 tion of the recess arch. 
 
 101... Semi-detached walls, Fig. 2S, are also, in some cases, 
 built with recesses. Besides these, traverse walls, Z7, are built 
 back from the scarp wall into the parapet, at intervals, to 
 afford cover to the troops, circulating in the corridor, from 
 enfilading tire, and to admit of a defence of the corridor it' 
 the assailant should enter it between any two of these tra- 
 verses. For this purpose they are pierced with loop-holes, and 
 have door-ways for circulation throughout the corridor. 
 
 102... In the more recenl fortifications built in Germany and 
 the north of Europe, a frequent use has been made of detached 
 scarps. They present a double obstacle to an escalade, as the 
 lant. having gained the top of the wall, has .-till to descond 
 ou the other side* They would probablj be more easily 
 breached than the ordinary scarp revetements with counter- 
 forts; and from some experiments made in England, with a 
 view of ascertaining the resistance <>t these walls and the 
 r given them by earthen masks, arranged in a manner 
 similar to - rman fortifications, it is questionable 
 
 whether, with the heavier calibre now coming into use in sit 
 and the improvement of late year.- in their range, such walls 
 might not be readily breached from a distai 
 
 L03.JTh« partly detached scarp wall, with relieving arches, 
 would seem to offer the advantage of more security from 
 calade than the old scarp wall, as the assailed are in a better 
 
:>-J. ELEMENTS OF PERMANENT WORKS. 
 
 orridor to drive the assailant back than when 
 placed behind the parapet. It offers all the difficulties to 
 bn aching of the full scarp with relieving arches, and presents, 
 whm the breach is rendered practicable, a narrow defile 
 through which the assailant must force his way into the work; 
 whereas, when the wholly detached scarp is overthrown, the 
 !ant may enter with any front he may choose, as the only 
 obstacle then in his way will be that of the height of the ram- 
 part and the steepness of its exterior slope. 
 
 1<'-1...S< aim- Galleries. In the permanent works of more 
 recent construction in our own country ami in Europe, revete- 
 ment Malls, with relieving arches, PI. 4, Fig. 15, have, in most 
 -. been introduced instead of the ordinary thick walls, with 
 counterforts, which had been hitherto the usual mode of re- 
 taining the earth of the rampart and parapet. 
 
 lo.".. ..The piers of the relieving arches, which also serve as 
 counterforts to the revetenient wall, are rectangular in plan, 
 and usually ran hack from 12 to 16 feet. They are from 4 to 
 t thick, and placed from 12 to IS feet apart between their 
 centre lines. The arches are usually full centre, and two feet 
 thick, with a roof-shaped capping, which adds an additional 
 thickness from !♦ to 12 inches over the crown of the arch. 
 
 lot;. ..The preceding Figure is a section of a revetement 
 wall of this kind, of one of our forts, though the curtain in 
 front of which is a mask, of which 1) is the section. A\ is an 
 elevation of the face of the pier; C, the relieving arch; and 
 J, the scarp wall. 
 
 1 < '7.-/11 1 i- mode of construction offers the advantages of a 
 more Stable structure, and rendering it more dimcnll for the 
 
 assailant to make a practicable breach in the wall, whilst, by a 
 BUltable arrangement of the relieving arches and their piers 
 w ith the earth of the rampart, a sullicieiil space can be secured 
 
 behind the Bcarp wall to form a gallery for defensive purposes. 
 l08...The arches and piers form the top and sides of the gal- 
 lery, the scarp wall forming the front, and the back or rear 
 
 being either partly or wholly closed by a wall which retains 
 
COMPONENT ELEMENTS OF PERMANENT WORKS. 
 
 the earth behind it. The gallery is thus divided ap into 
 chambers, Hie communication between which is effected by 
 door-ways made through the piers. 
 
 109.. .The width and heigh* of the gallery should in all oases' 
 be sufficient to allow the men ample room tor handling their 
 fire-arms, and to admit <>t' a circulation through the gallery, 
 when the troops for the defence are posted in it. 
 
 1 in. ..From three to tour Loop-holes are made in the portion 
 of the scarp wall that forms the 'front of each chamber. The 
 dimensions and forms of the loopholes are the same as already 
 described, and they are otherwise arranged for defence as in 
 detached scarp Malls. 
 
 111. ..In PI. 4, Fig. 1(!, a section of a scarp gallery cOtt^ 
 strncted in one of our forts is shown. A, is the scarp wall; 
 B, the pier of the relieving arch, C ; I), the rear wall which 
 closes the gallery and sustains the earth behind it. Tlie sec- 
 tion also .-hows the parts of the rampart and parapet, and the 
 breast-height wall. /•/. 
 
 1 1 •_'... In Figs. 17. I s . 19, the plan, section and rear elevation 
 of a gallery is shown as given in French authorities. The. 
 peculiarity of this example, Fig. 1!', consists in the arrange- 
 ment of the rear of the gallery, which instead of being en- 
 tirely closed by a wall is only partly so; a small wall, «, 
 which rests upon an arch, I, lmilt hctween the two pier 
 placed parallel to the hack of the scarp wall, and at a distance 
 from it equal to the width of the gallery, the top of the wall 
 being raised to the level of the surface of the earthen si 
 which falls in behind from. ..the top of the arch. The section. 
 1^. through r *, ami elevation, Fig. L9, show the position 
 
 of the loop-holes, and the vent for the escape of the stftoke, 
 which i> pierced in the scarp wall just below the crown of the 
 arch. By are th< be arches with their capping; Ik 
 
 the door-ways through the j, ; , 
 
 11.".. 0, 21, represent the plan and sectjon of a 
 
 gallery in two ti> ren in an Austrian work. The i 
 
 of the gallery is closed by ■ Bimple wall, !■ the vent- 
 
.". I ELEMENTS QF ri:i:M.\M:.NT WO8K0, 
 
 boles for the escape of Binoke, drains arc made in the scarp 
 wall, at the li'\* 1 of the gallery door, to convey off any water 
 that may collect in it. 
 
 114.. .!':_-. 22, 23, arc a plan and section, from the same 
 authority, of a gallery behind the lower portion of the scarp 
 wall, the upper portion being connected with relieving arches, 
 so arranged that, being open to the rear, the* foot of the Blope 
 of earth will just touch the back of the wall at its foot within. 
 Jn this example, the pressure of the earth being supposed to be 
 
 •. the gallery is closed in the rear by arched walls; the 
 
 arches being built into the vertical piers, Z?, of the relieving 
 arches, ('. This example also shows the manner of barricad* 
 ing the door-ways through the piers by vertical grooves, made 
 
 in the opposite faces of the piers, to receive the scantling ibrin- 
 ing the barricade. 
 
 115.. .In Fig. 28 is shown the section of a gallery behind the 
 lower portion of the scarp, with the upper portion arrange 1 
 with recesses for loop-holes. 
 
 llG...C\>r.\T]:i;x arc (i.M,i.i:i;ii>. PI. -1. Fig. 35. The most 
 simple method <>!' arranging a gallery behind a counterscarp 
 wall, for the defence of a ditch, is to build another wall par- 
 allel tu that of the counterscarp, and to throw an arch over 
 between the two to cover the top of the gallery. The counter- 
 scarp wall is pierced with loopholes* arranged in the same 
 way as in scarp galleries. 
 
 1 1 7. ..The example selected is from one of our works, and 
 shows a section of the gallery through a loop-hole. -1, 
 counterscarp wall; D, parallel wall; (7, arch and capping; E, 
 glacis mask covering the scarp wall. 
 
 lis. ..In Fig>. 1".), P>0,31, are shown a plan, section on r 6, 
 and a section and interior elevation on fljp, of a counterscarp 
 gallery taken from a French authority. In this case counter- 
 forts, Bquare in plan, are built along the back of the counter? 
 Scarp wall, leaving 8 feet between them. Parallel to the 
 counterscarp .wall, and 4 feet in rear of the counterforts, 
 another wall is built, which, with the counterforts, serves as 
 
COMTONENT ELEMENTS OF 1'KIIM A M AT WOBK.S. 55 
 
 tlic support of a scries of arches perpendicular to the counter- 
 scarp wall, sprang between tin- counterforts, and another 
 parallel to it and resting on the counterforts and parallel wall. 
 The arches between the counterforts form, with them, re- 
 I, for the men serving the loop-holes, pierced in the 
 Counterscarp wall; whilst the covered space, />', in rear, servo 
 for circulation, without disturbing the men engaged in firing. 
 
 119.. .Counterscarp galleries may also be arranged for a ditch 
 defence with artillery — short guns, like carronades, being used 
 for this purpose. A plan, Fig. 32, a vertical section and side 
 elevation on D C, Fig. 88, and a section and hack elevation 
 on A B, Fig. 34, taken from one of our works, shows a dis- 
 position of this kind in the reentering angle of the counter- 
 scarp. 
 
 lL'<i...r,.wi I ,,NM is. In small works, where a flanking dis- 
 position cannot he obtained from the enceinte, as in Lunettes 
 and redoubts, the ditches may he swept by covered chambers, 
 Pi. 5, Fig. 39, attached to the scarp wall either at the centre 
 of tin- sides of the work or at the angles. 
 
 These chambers, PI. 5, Fig. 39, are usually of a pentagonal 
 form — the sides which join the scarp wall serving to flank it, 
 and the two exterior sides, forming a salient angle, delivering 
 their fire on the opposite counterscarp and it> crest. From 
 their form and purposes, they have received the name of 
 bastionnets. 
 
 The dimensions of these constructions will depend upon the 
 amount and kind of lire to be delivered. Their scarps should 
 be as high as that ot the main work. They Communicate with 
 the interior of the main work, either directly by gallery or 
 postern, or from a scarp gallery. 
 
 :;:» show.- a plan of a bastionnet, /A at an angle com- 
 municating with a scarp gallery, /'.'. In rear of the scarp 
 gallery, and opposite to the bastionnet, is placed a small 
 powder magazine for it.- service. The example is from Aus- 
 trian authority, and i- arranged tor one small gun on each 
 flank besides the loop-holes tor small arms. 
 
OOMPONKNI ELEMKNT8 O] PKRXAKENT WORKS. 
 
 121. ..As il rule, it may be laid down that the Balieiit 
 
 angles of the redoubt are the most suitable positions for the 
 bastionnets, as they will thus form small bastioned fronts, in 
 which both the Bides of the main work and those of the bas- 
 tionnet will be swept by the flanks of the latter. The only 
 danger in this arrangement is, that the loop-holes in one Hank 
 may be fired into from the opposite one. This, however, may 
 be guarded against by a suitable position given to the loop- 
 holes. 
 
 L22.. .As the main object of covered defences is protection 
 against shells, it is essential that the arches of the galleries 
 an.d bastionnets should be bomb-proof. As the Bpan of these 
 arches is usually small, a thickness of 2 feet given to the 
 masonry, and a covering from 4 to 6 feet of earth above it, is 
 
 ordinarily considered sufficient for the object in view. 
 
 123. ..With regard to the front walls of these constructions, 
 as they are too thin to withstand the direct action of artillery, 
 they must either be covered by earthen masks, as a glacis 
 raised beyond the counterscarp for example, or he used only 
 in positions where they are not e.xposedto this tire. 
 
 1 J 1. ..It should be observed that whatever advantages cov- 
 ered defences afford as shelter from the assailant's fire, they 
 present the inconveniences of a comparatively narrow and ob- 
 structed iield of view to the assailed, which is further obscured 
 by the smoke, which may gather within the gallery, and in 
 front of the loop-holes. From these causes the assailed having 
 to aim at a venture, his fire is likely to be less effective than 
 in open defences where the smoke disperses rapidly and leaves 
 a (dear Held of view. The same may be said of loop-holed 
 Avails covering exterior corridors where the space to the rear 
 is confined. 
 
 Owing to these considerations, loop-holed and covered de- 
 fences of the kind in question should be restricted to special 
 defensive purposes, where an object within the held of fire 
 can be attained with some certainty, whether seen or not by 
 the assailed; as, for example, the protection of a ditch, or a 
 
 4 
 
COMPONKNT ELEMENTS OF PERMANENT WORK8. 57 
 
 scarp wall which cannot be flanked from within the work for 
 sweeping a covered-way, or the interior of any outwork which 
 cannot be brought well under the tire of the parapet of the 
 main work. 
 
 125...Caponniekk Defences bob the EnckinTE Ditch — 
 These works are classed under the head of what are termed 
 defetvsive casemates, whick are bomb-proof arched structures 
 for receiving cannon, which lire through embraaurea pierced 
 in the front or mask wall of the casemate* Defences of this 
 class, when used to flank the main ditch, are usually termed 
 mated caponnieres. 
 
 1lm>... These defences arc usually placed in the main ditch at 
 the middle point of the side or front to he flanked. The out- 
 line of their plan is mostly that of a lunette, PI. 5, Fi^. 36 — 
 the flanks being perpendicular to the line of the scarp, and 
 the two face.- making a salient angle of 60°. The caponniere 
 is either built in juxtaposition with the enceinte, or else de- 
 tained from it. In the latter case, an enclosure is formed be- 
 tween the two by a loop-holed wall which connects the flanks 
 with the scarp wall. Each flank consists of one or two tiers of 
 arched chambers — the piers of the arches being perpendicular 
 to the hack of the walls of the think. Each chamber is of 
 sufficient dimensions for the service of a single gun with a con- 
 tracted field of fire, I']. 5, Figs. 36, -">7. In some cases, loop* 
 holes are pierced for small arms on each side of the embrasure ; 
 in others, the casemates of one story are pierced for cannon and 
 the other for small arms. 
 
 127. ..The <•.. are closed in rear by a thin wall, which 
 
 is provided with windows for light and ventilation; and the 
 piers are pierced with door-wavs, to form a communication 
 between the chambers and to assist the ventilation. Elm - 
 venfa, Fig. 37, are made in the front wall, just under the 
 arches, for a like purp — . Wnere it may be necessary, the 
 
 lower floor is drained by a Conduit through tlw front wall. 
 
 l- v ....\ lefl between the d each 
 
 flank rered at top with from 4 to 6 feel of earth, The 
 
KPONZNT ! l.l MINT.- OF Ti:i;M.\Nl'NT WORKS. 
 
 flani parated from the faces by a closed corridor, which 
 
 communication. 
 
 1 •_".'. ..In front of the corridor and on each side of the axis of 
 the caponni6re, a easemated chamber, which is open in front, 
 ia arranged for one mortar, Pigs. .'!»'>. -'I s . The arches of these 
 ehambers rise toward the front, the better to subserve the ob- 
 ject in view. 
 
 130. ..On one side of the chambers the powder magazine is 
 placed, with a store-room. On the other side a stair-way be- 
 :i the stories is built. 
 
 131. ..The space within the salient angle, enclosed by the 
 walls of the faces and the front of the mortar casemates, is 
 open at to] >. It has an open corridor for communication, and 
 the front walls are arranged with loop-holed recesses for small 
 arms, Figs. 36, 38. 
 
 132. ..The enceinte, in rear of the flanks of the caponniere, is 
 arranged with a scarp gallery, to flank the caponniere flanks 
 and the court between them. A break is, in some cases, made 
 in the line of the scarp wall, pWpendicular to the caponniere 
 laces, and casemates for cannon and small arms arranged be- 
 hind the scarp wall to flank these faces. In some cases these 
 flanking dispositions are placed in front of the scarp wall, the 
 casemates being open to the rear, looking on a narrow court 
 between them and the scarp which is closed on the sides by a 
 loop-holed wall. 
 
 133. ..The example here given of a casemated caponniere is 
 from an Austrian authority. Fig. 36 is the plan; Fig. 37 a 
 section and elevation on A £ of one flank and the end wall of 
 the corridor looking toward the court between the flanks ; Fig. 
 38 a section and elevation along 0' D' of the corridor, mortar 
 casemate and triangular court ; Figs. 37, 38, are on an en- 
 larged scale. 
 
 134... Casemates on Land Fronts. Various modes have, 
 from time to time, been proposed for arranging defensive case- 
 mates lor the exterior defence on land fronts. The difficulty 
 in covering the masonry from the batteries of the assailant has 
 
niMi'iiNKXT ELEMENTS OF PERMANENT WORKS. 59 
 
 been the chief objection to these structures, and is the more 
 prominent as the fire of artillery becomes more accurate, as 
 such casemates would soon be ruined or rendered untenable 
 bj T embrasure shots. 
 
 135. ..The structure for this purpose which has been most 
 applied within late years, is what is termed the Haxo casemate / 
 the details having been first proposed by General Haxo, one 
 of the first authorities of the French school of engineers. 
 These casemates consist, Figs. 45, 46, 47, of a series of arched 
 bomb-proof chambers; dosed in front by a thin mask wall, 
 which^exeept around the embrasures through it, is covered 
 from Wk assailant's artillery by the parapet. To present but 
 a small surface of masonry to fire, the arches, which are hori- 
 zontal and perpendicular to the mask wall for the greater 
 portion of their length, descend toward the front, leaving, 
 where they join the mask wall, just sufficient height within for 
 the service of the gun. To effect this, the anterior portion of 
 the arch must be conoidal in shape, 
 
 13G...The piers of the arches are pierced with wide arched 
 openings, which serve the double purpose of a communication 
 between the casemates and to give the gun a wider traverse 
 for firing. 
 
 137... Embrasures are pierced in the parapet in prolongation 
 of those of the mask wall, and it is proposed to cover the 
 small portion of the masonry necessarily exposed by this ar- 
 rangement, by placing several thicknesses of heavy timber in 
 front of it to receive the shot. 
 
 138. ..When the casemates serve simply for the cover .of the 
 
 cannon, the arches are covered with (torn 4 to 6 feel thickness 
 
 of earth, and are left open to the rear for rlie more prompt 
 
 ]><■ of the smoke, and ■ ditch is sometimes made jusl in 
 
 ^rear of the casemate* to ditch bombs ami limit the effects of 
 their explosion. When the arches are made longer than for 
 the service of the guns alone, the earthen covering is sometimes 
 arranged with a parapet to cover cannon in barbette, or for 
 
 ■ •- 
 
IfPONBHT - CW !'I:i:ma.mnt WORKS. 
 
 l39...The examples shown by*' the figures is from a French 
 authority. Fig. 45 is a plan od m n, Fig. 17 : Fig. 46 a - 
 tion and interior elevation toward the mask wall on o y, Fig. 
 47: and Fig. 17 a section ami Bide elevation on /• *, Figs. 
 45, 46. 
 
 14".. .In Figs. 48, 1!', is shows an arrangement of two case- 
 mates of the Haxo kind, from an Austrian authority. In this 
 case, tin 1 masonry is covered on the flanks from enfilading fire 
 1>\ earth. Fig. 48 is an interior elevation of the arches, and 
 the hack wall that retains tile earth on the sides. Fig. 49 is a 
 Longitudinal section, and shows the maimer of cove^ng the 
 masonry in front and securing the earthen embrasiPb by a 
 timber facing. 
 
 141...MobtaE C askmatks. In Fig. 50, PI. 6, is shown a 
 longitudinal section of a mortar casemate placed in rear of 
 a parapet, by which it is covered from direct fire. The arch 
 is covered, as in the preceding case, by earth, to break the 
 shock of shells. It rises toward the front, to give ample room 
 for the shell in its flight. The casemates are covered on their 
 flanks from enfilading fire by an embankment, and are partly 
 closed by a wall in rear. A small ditch is made in front of 
 the chamber, and a slight wall built within it, to give cover 
 from the splinters of shells falling between the parapet and 
 casemate 1 . Arched chambers are, in some cases, made beneath 
 the mortar chamber, which serve as store-rooms and temporary 
 magazines. 
 
 142. ..When these casemates are placed in rear of a portion 
 of the parapet, but little exposed to direct fire, the thickness 
 of tlie parapet in front of them may be reduced, and the in- 
 terior slope lie replaced by a breast-height wall along the front 
 of the casemates, in order to give better cover in flank and 
 from slanl lire, by throwing forward the casemates more undent 
 cover of tin' parapet. 
 
 1 l3...The example given is from the same authority as in 
 the preceding example of casemated caponnieres. 
 
 I 1 L. Casemates foe Water Fronts. In the casemated bat- 
 
 
 M 
 
COMPONENT ELEMENTS OF l'KUMA.NKNT WORKS. 61 
 
 terics for sea-coast and harbor defence, the scarp or mask wall 
 of the chambers for the guns, being exposed to the iire of 
 ships alone, are not covered^ as on land fronts, by an earthen 
 mask j these walls being built of sufficient thickness and 
 strength to withstand the lire of the heaviest guns within the 
 range that .ships can venture 1<> attack, and being far less vul- 
 nerable than the wooden or iron sides of vessels thus far 
 brought into general use. 
 
 145. ..These batteries, in our own and European works, con- 
 sist of a series of arched bomb-proof chandlers, which serve 
 for the service of the guns alone; or else the}' receive such 
 dimensions that the portions <>t' the chambers immediately in 
 rear of the mask wall arc appropriated to the service of the 
 batten, and the rear portions are converted into quarters, 
 store-rooms, and other necessary purposes for the garrison. 
 
 1 Hi. ..In the earlier sea-coast casemated defences constructed 
 in onr Bervice, the gun chambers have received dimensions to 
 admit of two guns in each chamber, PL 5, Figs. 4<>, 41. The 
 chambers are usually formed of segmental brick arches of 
 L20°, which rest upon 6tone piers built back perpendicular to 
 the mask wall. In the example given, the arches, C, have a 
 uniform thickness of 3 feet, exclusive of the roof-shaped cap- 
 ping, which i> generally of rubble and betoii. and which is 
 red on top by the earth «»f the parapet ami rampart. The 
 
 /»'. are frf f.-ct thick, and are pierced with arched 
 
 communications, /•". a few feet in rear of the mask wall, 
 placed as to give the gun-carriage a wider traverse by allowing 
 it to run under this opening. Arched recesses, /.'.are made in 
 the mask wall t.» admit the muzzle of the gun being well run 
 out. bo a.- to clear the casemate <>t' smoke. An embrasur 
 i> pierced at the centre of each receBS, the sole being at the 
 proper height above ii l( . floor of the casemate, to accommod 
 the casemate chassis and top carriage. In Pig. 40, i.- shown 
 the plan and dim >f the embrasures usually adopted in 
 
 onr works, until . and in Fig. J], whid 
 
 n vertical section of tin casemate through the axis of an em 
 
 «.*■ 
 
62 OOMPONENl ELEMENTS OF riKMAM.vr WOBES. 
 
 lira-ure. is shown tin' elevation and dimensions of the cheeks; 
 ,, of the embrasure. In the casemates of Borne of owr works, 
 flues for ventilation and carrying off rapidly the powder smoke, 
 run from t}ie top of the carriage recesses, /.', through the ma- 
 sonry of the scarp wall, and have their outlet in the top of the 
 wall. In others, the fines run from the casemate arch to the 
 top of the parapet. Peneath the embrasure a recess, termed 
 the tongtte-hole^ which in plan is triangular, is made to receive 
 the tongue of the chassis. The tongue is confined in it&place, 
 and the chassis traverses around a pintle which is received into 
 the pintle-hole, made at the centre point of the throat of the 
 embrasure, ami extending into the masonry below the tongue* 
 hole. 
 
 147. ..When the casemates serve also as quarters for the gar- 
 rison, the rear, toward the parade, is closed by a brick or stone 
 parade wall, which forms the front wall of the quarters. A 
 brick partition wall separates the quarters from the gun gal- 
 lery. Arched recesses and flues are made in the piers for 
 chimneys ; and the parade wall, the sides of the piers, and sof- 
 fit of the arch, are suitably finished to give a dry and well 
 ventilated dwelling. 
 
 148.. .In the example here given, as in most of our earlier 
 casemated works, there is but one tier of casemated guns ; this 
 tier being surmounted by a barbette battery, covered either Ivy 
 an earthen or stone parapet on the water fronts. 
 
 1 !'.»... Casemates adapted to two guns in each room, present 
 a more vulnerable mark in the portion of the mask wall be- 
 tween the piers ; expose more men to danger from embrasure 
 shot> : present a greater opening, in rear, to the assailant's fire, 
 when not closed by a parade wall ; offer less resistance to the 
 shock of shells, and are more difficult to construct, without 
 settling, than rooms for single guns. These advantages in 
 favor of casemates for single gnns are the more marked where, 
 tor the purpose of obtaining a heavy fire in some fixed direc- 
 tion, it is desirable to resort to a castellated structure, consist- 
 ing of several tiers of casemates. 
 
COMPONENT ELEMENTS OF. PEBMANENT WORKS. C>3 
 
 150.. .In PL 6, Figs. 42, b), 4 t, is shown ft plan. Fig. 42, on 
 E F, of the first tier of casemates; a vertical section and side 
 elevation, Fig. 43, on A B, of the three tiers of casemates and 
 the top barbette battery ; and, in Fig. 41, an interior elevation 
 on CD, of one of the most recent of these structures for the 
 defence of the channel leading to one of onr harbors. Besides 
 the wide arched openings F. through the piers, for communi- 
 cation and the traverse of the guns, smaller door-ways, a, arc 
 made for communications in rear of the battery. The case- 
 mates are Open in the rear. The arches of the top tier are 
 alone made bomb-proof; those of the lower tiers receiving suf- 
 ficient strength to receive the armament and admit of the ser- 
 vice of the guns with safety. 
 
 15L.J£mBbaSUBES. The form, dimensions and construction 
 of embrasures in mask walls, present a problem which has of- 
 fered no little difficulty, in a satisfactory solution, toengim 
 by which the best coVer could be given to the guns and men, 
 by exposing the least surface to embrasure shots, whilst the 
 guns should receive a suitable traverse to command a wide 
 field of fire. 
 
 152. ..In the embrasures of our works the general form is the 
 same as those usually found in Europe, but they present a very 
 considerable less amount of exterior and throat-opening than 
 European embrasures. See PL 7. Fig. 59, which is the plan 
 of a French carriage recess and embrasure for a Bingle gun. 
 and Fig. ''-'I, which is one of the same parts of an English fori 
 for sea-coast defence. In some of onr earlier works, the sole, 
 cheeks and top of the embrasures are constructed of brick, as 
 being a material thai would be less destructive through the 
 splinters driven in by embrasure shots. This view, however, 
 has been abandoned in our more recent works, the embrasures 
 being constructed, on the contrary, of heavy stone blocks, 
 cart fully and Strongly bunded; a brick arch being thrown 
 above the embrasure, within the mass of the mask wall, to 
 secure the upper portion from yielding should the block form- 
 ing the ceiling of the embrasure be damaged. 
 
 
64 ELEMENTS "'' r: kmanknt WOBXB. 
 
 153...A further and most important step lias been more re- 
 tlj taken, in the application to embrasures of wrOnght-iron 
 and throat-pieces, with shutters <>i" the same mar, 'rial, 
 linst heavy ahol and grape. The first applied 
 ■ it' this means has been made to the embrasures of on 
 works now in the course of "Construction ; and the forms, 
 dimensions and construction of the embrasures are the results 
 of experiments carefully made with the heaviest solid shot and 
 -rape, upon walls and embrasures of various forms and dimen- 
 sions, under the directions of General Totten, chief engineer- 
 
 1.". I. ..The form adopted is shown in plan in IM. S, Kin-, ill — 
 tin- interior portion being trapezoidal, and the exterior, beyond 
 the throat, rectangular. This form was adopted with the 
 double view of limiting the effects of embrasure shot, which, 
 in the old forms, striking the oblique surfaces of the cheeks of 
 the exterior portion and. glancing inward, occasioned consider- 
 able casualties, and to form a suitable recess for strong iron 
 shutters to protect from grape entering through the throat 
 whilst the gun was out of battery. The tw6**principal wrought- 
 iron throat-pieces are trapezoidal in plan, being 8 inches thick 
 and 17 inches base, the oblique side having the same slant as 
 the inner cheek of the embrasure. Exterior to these two 
 pieces are two plate-pieces, each two inches thick, against 
 which the shutters, which are also two inches thick, rest when 
 open or closed, as shown in Fig. 01. There is also a wrought- 
 iron plate casing around the exterior opening of the embrasure, 
 as shown in Fig. 61, and in the exterior elevation. Fig* (!4. 
 In Fig. G2 is shown an interior elevation of the carriage recess, 
 the embrasure, and the tongue-hole ; and, in Fig. (!3, a verti- 
 cal section and siiK' elevation on A B, Fig. 64, of the embra- 
 sure, carriage recess, and the pintle and tongue-holes. 
 
 155... The exterior width of the embrasure, the obliquity 
 given to the cheek.- of the interior portion, and the depth and 
 slant given to the carriage recess and its sides, are arranged 
 with a view to the traverse of the gun, which is fixed at o'0°, 
 or 3<>° on each side of the axis of the embrasure. 
 
COMl'o.NKNT ELEMENTS OF PERMANKNT WORKS. 05 
 
 156. ..All the parts of the wall adjacent to the embrasure are 
 constructed of the largest sized blocks of the toughest stone, 
 the blocks being carefully fitted and bonded, and having the 
 additional strength afforded by a very ingenious arrangement 
 of hollow bolts, and a concrete of lead and ehippings of stone 
 run together. A brick arch, as shown in the elevations and 
 sections, is turned over the embrasure and within the mass of 
 the scarp wall. 
 
 157...Bomi;-j>roof Bnr.mxos. Casemated bomb-proof quar- 
 ters are indispensable to the safety and comfort ofthe garrison 
 during siege or any prolonged attack for the annoyance or re- 
 duction ofthe work by a bombardment. In small works like 
 the most of our forts, which are chiefly designed for sea-coast 
 defence, casemated quarters are arranged as has been seen in 
 the rear of the batteries, a portion of each casemate toward 
 the parade being partitioned off and suitably disposed for the 
 object in view. In some cases advantage is taken of a scarp 
 wall, on a land front, which is well covered by a glacis or 
 other face cover, to form in its rear quarters of this character. 
 In all cases, care should be taken to place such quarters on 
 those fronts which are best covered from a direct fire, and the 
 parade walls of which are not exposed to reverse fire. When- 
 ever the plan of the work admits of it, quarters of this kind 
 should he arranged for defence, by being pierced with loop- 
 hole.-, and even with embrasures for cannon. Defensive case- 
 mated quarters form a prominent and distinctive feature in 
 what is now known as the German school of permanent fortifi- 
 cation. They consist of bomb-proof buildings of a curvilinear 
 or polygonal plan, arranged for one or more Btories of covered 
 defences, with an ordinary open defence surmounting tin- 
 ca>emates. The casemates of the upper story are covered by 
 bomleproof arches, whilst those of the lower Btories re© 
 flal segment arches of only sufficient thickness and strength to 
 
 bear the Weight of the guna and to subserve the other ol.j. 
 
 of the structure. When employed a.- caponnien 
 defences, or as interior retrenchments, the front walls of ti. 
 
IIIMI Ni- OF PERMANENT WOKS. 
 
 structures are masked from direct views, either by the glacis 
 or by the parapel of the work in which they are placed, and 
 they receive a thickness of at least 5 feet. But as a mask 
 Avail even of this thickness, When pierced with loop-holes and 
 embrasures, is liable to damage from shot which plunge over 
 the parapet in front <>i' it. PI 7. Fig. 53, the portions of the 
 mate piers, //, where they j< »in the mask wall, -1. are 
 made thicker, in some cases for a distance of a few feet hack, 
 than their general thickness, ! in order to receive two vertical 
 grooves in the face of this thicker portion, into which scantling 
 being inserted horizontally, and the Bpace between the two 
 partitions thufl formed filled in with sand-bags or other shot- 
 proof materials, a temporary shelter can be formed when the 
 rnin of the mask wall exposes the interior of the casemate to 
 view. 
 
 In our service, PI. 7, Figs. 51, 52, when casemated quarters 
 are constructed of two stories, the upper one alone is covered 
 with a bomb-proof arch, the floor between the two being of 
 timber, ami constructed in the ordinary way. 
 
 158.. .In Fig. 51 is shown a plan on A D, Fig. 52, of bomb.- 
 proof casemated quarters in rear of a scarp wall and of a 
 counterscarp gallery, both arranged with loop-holed defences. 
 Fig. 52 is a section and side elevation on CD, Fig. 51, show- 
 ing the rampart and parapet over the arch and tin 1 fireplaces 
 and chimneys in the piers of the arches. The floor of the 
 second story is of timber. The rear or parade wall is pierced 
 with doors and windows. 
 
 ir.it... In Fig. ;,:; is shown the plan of the end of a casemated 
 defensive barrack, from an Austrian authority. The front 
 wall, J, is arranged and pierced for cannon, each arched 
 chaniher for one gun. The end wall is loop-holed for mus- 
 ketry, and the rear wall, ( \ has windows and doors. 
 
 160...PowDfBB Magazine. The structures for this purpose 
 
 built with strong, full centre, bomb-proof brick arches, 
 
 supported on heavy .-tone piers, which form the outward walls 
 
 and to which interior buttresses are sometimes added. The 
 
COMPOXKN I ELEMENTS OF HKMAMM WORKS. 67 
 
 capping of the arches is covered with from 4 to G feet of 
 solidly packed earth. The interior of the magazine, the Hours, 
 and the doors and windows, are built with a view to security 
 from fire; and to preserve the pow4er from dampness, by a 
 good system of drainage around the foundations, and of ven- 
 tilation by means of air-holes made through the piers, and 
 panels of copper pierced with smal] holes placed in the doors. 
 No iron or steel fastening or sheeting is allowed in any part of 
 the atrdature; and in arranging the air-holes through the 
 piers, they receive a broken direction ami have ;i copper mesh- 
 work placed across them, to prevent any combustible material, 
 or rats, or mice, penetrating to the interior of the magazine. 
 
 In large works the magazines are isolated, as far as practica- 
 ble, from the enceinte, so aa not to endanger it should an acci- 
 dental explosion take place. The magazine is enclosed by a 
 strong high wall for security, and is provided with lightning 
 rods. In small works some one or more of the casemates, in 
 the least exposed position to the assailants lire, is built for the 
 pur] loses of a magazine. 
 
 COMMTXICATIONS. 
 
 I61...The communications form a very important element in 
 the defence of permanent works. They consist of r<im]>s y 
 stairs. i.-ir.njs and bridges. 
 
 162...Ramp8. Ramps are inclined planed, or path.-, leading 
 from one level to another, aa from that of the parade to the 
 
 plein of the enceinte. Their width at top, for thi 
 of the artillery and other vehicle.-, may he from 10 to 15 
 and their inclination from L-6 to 1-15, or less, depending 00 
 the difference of level to he overcome. They are usually 
 placed in positions where they will occupy the least room of 
 the j ilong the rampart-slope of the enceinte. A- a 
 
 ral rule, th< earth ; but wh< 
 
 ■ m on the parade, ti 
 replaced on one or botl . wall which the 
 
Pi KMANKNT WOT 
 
 th of the ramp. When rani]'- serve for infantry alone, thoir 
 
 width may be reduced to 6 feet, and in some cases to 4- feet. 
 
 L68...Stajbs> Stairs, except for temporary purposes, are 
 
 structed of atone; efcch step being a Bolid block which is 
 
 t Long in the clear: its breadth at top or the tread li' 
 
 inches, and its height or rise s inches. Stair.- are nsnalfy 
 
 along the counterscarp and gorge walls of the outworks, 
 
 forming a < imunication. for infantry only, between the ditch 
 
 and the terreplein of the work to which they lead. They are 
 used within the enceinte in positions where there is not 
 sufficient room for ramps; or where; for greater security from 
 surprise, it is desirable to present a narrower and more difficult 
 defile to the assailant. In cases where room is wanting and 
 the communication not in habitual use, the width of the stair- 
 way may be reduced to 4 feet. 
 
 164...Po8TERNB. Posterns are arched passage-ways con- 
 structed under the terrepleins and ramparts, forming subterra- 
 nean communications between the parade and the enceinte 
 ditch, or between the ditches and the interior of the outworks. 
 The width and height of the interior of posterns depend upon 
 the use to which the communication is to be applied. For 
 artillery, the width is usually taken at LO feet, and the height 
 under the crown or key of the arch at least s feet. Posterns 
 for infantry may be only from 8 to 4 feet wide, and from 6 
 feel 6 inches to 8 feet high under the crown of the arch. The 
 
 thickness of the piers of the arches is generally taken at about 
 half the width of the postern. The arches are from 18 inches 
 to 2 feet thick. As any injury to the arch from the bursting 
 of a shell over it might obstruct the communication, the arch 
 should he Covered with a thickness of at least )! feet of earth, 
 and. when convenient, with o or 6 feet for greater security. 
 A Btrong wooden door i^ placed at each outlet <»f the postern 
 to secure it against surprise. The door-way in posterns for the 
 of artillery should he of just sufficient height for the 
 convenient passage of a gun — about 7 feet for each dimension 
 IB usually allowed for this purp 
 
OOMPONENT KT.KMKNTS OF I'KUMAM'.XT WORKS. fi9 
 
 165. ..The most important postern is the one. leading from 
 the parade to the enceinte ditch. This generally recen 
 width of 12 feet, and the same height under the crown. For 
 {greater security from surprise, its outlet at the enceinte ditch 
 is at least 6 feet above the bottom of the ditch — this difference 
 of level being overcome by means of a temporary wooden 
 rani]), which receives an inclination of at least 1-6. With a 
 like object, besides two strong doors at the two ends of the 
 postern, there is a partition of masonry ahout midway between 
 the two ends, which is pierced with a door-way of the same 
 size as the door-ways Df the ends, and closed by a strong door, 
 which, as well as Hie partition wall, is loop-holed for musketry. 
 
 166.. .In cases where the postern forms the main entrance to 
 the work, an arched chamber is placed on one side of it, at the 
 outlet, which serve! a- 1 guard-room for a few men, to secure 
 the outlet from surprise. The wall between this chamber and 
 the postern is loop-holed, so that a fire can be brought to bear 
 on the door-way of the postern : and. as a farther precaution 
 against surprise, a machicoulis defence is sometimes arrai 
 at the lop Of the scarp wall just above the door-way of the pos- 
 tern. 
 
 1»;7...(, mi-way. In works with large garrisons, where the 
 means of frequent communication with the exterior are requi- 
 site, posterns of the ordinary dimensions are found not to afford 
 
 ifficient convenience for the daily wants. In such c:i - 
 way of sufficient width to admit of at least a single 
 carriage road, with narrow foot-paths on each side, has to l>e 
 
 ned through the rampart, which, whenever it is practicable 
 to d iild be niched, and covered with earth to ren< 
 
 bomb-]. roof. This passage-way shoul 1. fi ity, have the 
 
 bottom of it- outlet at least 12 feet above the b 
 enceinte ditch ; and when this difference of level cannot be 
 obtained, the main ditch should be deepened sufficiently for 
 Ike purpose below the outlet. A sufficient height 
 
 and width for the pa the ordinary \ , hiclea for th< 
 
 vice of the . is mad* 
 
OOMPOXEHT ELEMENTS OF PEBMAXENT WOfl 
 
 gate-Way is arched at top, where a machicoulis defence may 
 also be arranged to guard the outlel on tiw exterior. 
 
 L68...The communication across the enceinte ditch, Leading 
 from the gate-way, is usually an ordinary wooden bridge built 
 on piles. The bay of this bridge at the gate-way is spanned 
 by a drawbridge of timber, which when drawn up, closes and 
 secures the gate-way. This drawbridge is manoeuvred by some 
 of the usual mechanisms employed for this purpose. 
 
 L69„.Pobtoulli8. When the gate-way is not preceded by a 
 ditch, and is, therefore, without a drawbridge, a barrier, termed 
 a j'oilcnUix, which can be lowered or raised vertically by 
 machinery, is sometimes added to secure the passage-way from 
 surprise* The ancient portcullis was a framework of heavy 
 beams, placed vertically, leaving a few inches only between 
 each pair of beams. These vertical beams were either solidly 
 confined between horizontal beams, or clamping-pieces in 
 pairs; <>r else they were so arranged that they could slide up- 
 ward between the clamping-pieces. Each of the vertical 
 beams was shod at the bottom with a strong pointed iron 
 shoe. The horizontal pieces were framed securely with two 
 heavy vertical beams that formed the sides of the frame, and 
 were fitted into vertical grooves made in the side walls of the 
 passage-way, in which the frame could slide when raised or 
 lowered. By arranging the vertical beams to slide upward 
 between the clamping-pieces, it will enable the pa.-suge-way 
 to be closed in places where an obstruction might be design- 
 edly placed below the portcullis to prevent this being done; 
 ;is the beams which meet the obstruction would be pushed 
 upward, whilst the others would fall to their ordinary level 
 and close the passage-way on each side of the obstruction. 
 
 1 "<»... In the works recently constructed with us, the portcul- 
 lis, and even tlie doors preceding them, have been constructed 
 of a strong open lattice-work of wrought iron bars bolted 
 Btrongly to the wrought-iron uprights and cross pieces forming 
 the framework of the lattice. This is a great improvement for 
 these purposes, both as to durability and defence. 
 
ELEMENTS OV THE ri.AX of i:ncki.\tf.s and OUTWOEK8. 71 
 
 171... Passfi^c-wnys of tin's description should be secured by 
 all the means at an engineer s disposal. A largei guard-room, 
 
 with loop-holes bearing on the passage, should he erected on 
 one side, near the gate-way ; and if the enceinte is a simple 
 one, without outworks beyond its ditch, a small lunette, or a 
 loop-holed tambour of masonry or timber, should he con- 
 Btrncted beyond tin- counterscarp, forming a tele~de~pont, for 
 the security of the bridge from surprise. 
 
 1 7l\. .The drawbridge, which for convenience of manoeuvring 
 should not be longer than 12 feet, is constructed in the usual 
 mode. Care should be taken that it shall fit the recess in the 
 face of the wall so closely that there will not he room enough 
 between it and the jambs of the gate-way to insert an iron 
 lever to force back the bridge. 
 
 ELEMMS OF THE PLAX OF EXCE1MES AXD OUTWORKS. 
 
 KM KINTKS. 
 
 17". ..The most simple mode of fortifying a position in a per- 
 manent manner. in enclosing it with a rampart, 
 mounted by a parapet with a ditch, the Scarp of which, when 
 
 dry, ia revetted with masonry, and bo covered by an earthen 
 b that it cannot lie breached except by batteries placed on 
 the bord< r <>f the counterscarp. 
 
 174... An enclosed tine of fortification of thig simple charac- 
 ter is termed the /„„/// <■/ 
 
 

 
 rl BLEMENT8 OF THE I'l.AN OF ENOBINTES AM» OtTTWOB 
 
 175...The general outline of tlic enceinte may be curvi- 
 linear, or a polygonal figure of any character, 
 
 17'-...Sy-ii m of Fortification. Although an infinite diver- 
 sity of figures may thus be presented in the outline or plan of 
 the enceinte, they may be all classed under four heads, to each 
 of which engineers generally have applied the term, system of 
 fortificatibn. These four classes are: 1, the dircular or cwrWr 
 linear system ; 2, the polygonal or caponn'u" r<- system ; 3, the 
 A n i tilled system • 4, the bastiorud sysU m 
 
 177.. .The term method of fortification, instead of system, "is 
 now usually applied to the manner of fortifying, which is gen- 
 erally prevalent in anj T country ; or to the mode adopted by 
 any individual, as the German method, Y<iul>an' > s method, etc. 
 
 178. ..Circular System. The circular system consists of an 
 enceinte, the plan of which is circular, or curvilinear. 
 
 179. ..Polygonal System. In the polygonal system, the plan 
 is'either a polygon, with salient angles alone, PL 8, Fig. 72, 
 each side of which, A A, is flanked by a casemated capon- 
 niere, C, placed in the ditch, D, and midway between the two 
 salients, A / or else each side of the polygon is broken in- 
 ward at the centre, so as to form a slight reentering, PL 8, 
 Figs. 73, 74,75, 76, 77, to procure a casemated flanking ar- 
 rangement, F F, for the caponnieres, C, which occupy these 
 reenterings, and also, in some cases, to flank works in advance 
 of the enceinte. 
 
 180.. .Tenailled System. The tenailled system, PL 8, Fig. 
 78, consists of a tenailled line, the reentering angles of which 
 are between 90° and 100°, and the salient angles not less than 
 
 <;o°. 
 
 181...Bastioned System. The bastioned system, Fig. 79, 
 consists of lunettes or bastions connected by curtains, D 1), 
 between the extremities of their flanks, B D. The bastions 
 usually consist of two faces and two flanks, the scarps of each 
 of which are plane surfaces. In most of the older fortifica- 
 tions, and in a few of the more recent w T orks in Europe, the 
 flank is broken ; the portion of it at the shoulder angle form- 
 
i 
 
 OUTWORKS AND DETACHED WORKS. 73 
 
 ing a projecting mass, which is termed an orillo?i, whilst the 
 portion between the orillon and the enceinte curtain is re- 
 tired, or brought in toward the interior of the bastion, and is 
 thus partially covered by the orillon from fire, except in the 
 prolongation of the enceinte ditch. In some cases the plan of 
 the orillon, as well as that of the retired flank, is curvilinear ; 
 in others they are both rectilinear. 
 
 182. ..Front of Fortification. The term front of fortifica- 
 tion is applied either to the portion of the enceinte comprised 
 between the capitals of two adjacent salient angles of the poly- 
 gon, or to this portion and any other works within or beyond 
 it which are comprised between two adjacent capitals, and are 
 connected with this portion by relations of defence. 
 
 OUTWORKS AND DETACHED WORKS. 
 
 183.. .A work consisting of an enceinte alone is more or less 
 exposed to surprise, as it must have outlets of some descrip- 
 tion to keep up a communication with the exterior and a 
 bridge, or other means for crossing the ditch. But this is not 
 the only defect of a fortification of tins simple character; for, 
 having no cover.- beyond the ditch lor it.- garrison, their action 
 must be restricted to what may be termed a passive resistance 
 alone; as, in any attempt t<> operate on the exterior, they are 
 exposed to lire so soon as they emerge from the ditch; and in 
 a ntnat toward the work, if closely pursued by the assailant, 
 thi'Y will not only run tin- nali of being cut oil", but a reti 
 under such circumstances may lead to the capture of the work 
 10 
 
 
74 0! rWOXtXfl AM> DETACHED WOBSB. 
 
 itself, by the assailant being enabled to enter with the retreat- 
 ing force. 
 
 L84:..*.To provide against dangers of bo grave a character, 
 engineers have devised other defences beyond the diteh. and 
 which they have placed in Immediate defensive relations with 
 the enceinte, being under its fire and in positions where, if 
 assaulted, they can be readily succored by the garrison. To 
 this class of exterior defences the term outworks has been ap- 
 plied. The works which come under this head are the COM red- 
 way, the tenaill% the <hmihn<>\ the oourUerguard^ the r< doubt 
 or /•>'</>//'/. the 1> nii'ilhm* the Komwork and the cr(nc)i-tr<>rk. 
 
 l86.;.CovEEED-WAY. The eovered-wa v. SB its name imports, 
 
 is an open Corridor or passage, masked from the assailant's 
 
 view by an embankment, which borders the diteh of the en- 
 ceinte alone when there are no other outworks; but, in the 
 contrary case, also envelops the ditches of these, forming thus 
 a continuous covered line of communication around the for- 
 tification. 
 
 180. ..The covering embankment itself is arranged toward 
 the covered-way like an ordinary parapet, and it receives on 
 the exterior a gentle slope or glacis. By this arrangement the 
 garrison have a covered position beyond the ditch where they 
 can assembly with safety, either for the purpose of making a 
 sortie or to guard the ditches and the communications across 
 them; and which affords them also a secure point of retreat if 
 repulsed in a sortie, as a reserve left in the covered-way will 
 be at hand to. check the pursuit by their fire, and enable the 
 retreating party to gain the enceinte. 
 
 187... Flatus of Aims. The covered-way, from the direction 
 given to the counterscarps of the enceinte and outworks, forms 
 a line of communication with salient and reentering parts, Pis. 
 8, 9, Figs. 80 to 85. The salient portions, S, are termed 
 ealii n f places of arms ; and the reentering parts the reentering 
 places of arms. 
 
 188. ..The salient places of arms, it will be seen, result from 
 the general plan of the covered-way; but the reentering places 
 
OUTWORKS AND DETACHED WORKS. 75 
 
 of arms are formed by changing the directions of the two 
 brandies where they form the reenteringa, i?, so as to make a 
 salient within the reenteringe; thus enlarging the covered-way 
 at these points, and procuring a flanking arrangement, by 
 which the glacis can be swept, and a cross-fire be brought to 
 bear on the ground in advance of the salients. 
 
 1 s '.'...Tkavi;ksks. The covered-way, from its position and 
 the usually slight command given to the crest of its glacis, is 
 very much exposed to the effects of an enfilading fire. With 
 a view to remedy this defect, and also to enable the garrison 
 to dispute, foot by foot, the possession of this outwork by the 
 ilant, eartheni masks, formed like an ordinary parapet, and 
 termed traverses, are thrown up across it. The traverses 
 usually extend to the counterscarp, the wall of which is built 
 up to sustain them. At the end toward the glacis a passagttj 
 or defile, is left between them and the covering embankment, 
 to admit of a free communication throughout the covcred-wav. 
 
 190...Texaillk. The tenaille is a tow work, placed in the 
 reentering formed in the enceinte ditch by the curtain and 
 flanks of the bastioned system, being isolated by a ditch be- 
 tween it and these parts of the enceinte. Its chief purpose is 
 to serve as a mask, covering the scarp walls of this reentering 
 from tire, ib well as the Outlets to the enceinte ditch, which are 
 usually placed in the centre of the curtains. 
 
 L 91... The tenaille has received various forms from engineers. 
 In some cases it has been made with two laces or wil 
 making a reentering angle opposite the centre of the enceinte 
 curtain. In others the two wing-, instead of being proloi 
 until they meet, are connected by a abort curtain parallel to 
 that of the enceinte. In some examples, it has the form of a 
 small bastioned front. In others, it <■ ftwo flanks i 
 
 ted by a curtain. Tie- think.- in some cases have b 
 
 mated for guns and mortars. Tin b i aill< ; - asually 
 revetted with masonry, both in front and rear. In sou 
 
 the emb atone, toward the Hanks of the enceinte, an revetted, 
 
76 OUTWORKS \N" DETACHED WORKS. 
 
 the intermediate portions consisting of an ordinary earthen 
 parapet, without either scarp or gorge wall. 
 
 r.'i\..i>iMiu \r. The demilune, PL 9, Figs. 81, 82, S3. E 
 A.irk in the form of a redan, P. placed in front of the en* 
 
 eeinte curtain, which it masks from fire, as well as a portion of 
 cadi face of the enceinte, at the shoulder angles of the bas- 
 tions. It is isolated from the enceinte by the main ditch, and 
 from its own covered-way by its ditch. From its importance: 
 
 the scarp and gorge of the demilune are generally revetted, 
 though in Some cases the reveteinelit has heeii omitted*. 
 
 193...Cor.\Ti:i;(,r.\i:i>. The OOUnter'guard is an isolated work, 
 < '. Fig. 83, in the form of a redan, which envelops the faces of 
 a hastioft. In some cases it consists simply of an earthen mask 
 having the profile of an ordinary parapet; but it is usually 
 revetted botli in front and rear. 
 
 194.. .Redoubts. The term redoubt, or reduit, is applied to 
 outworks placed within other outworks; their object being to 
 strengthen the defence of the principal work. 
 
 195... A work of this class is usually placed within the demi- 
 lune, and is termed the demilune redoubt. Small works of 
 this kind are also placed in the salient and reentering places of 
 arms of the covered-way, and are termed the redoubt of the 
 salient) or reentering* place of arms. These redoubts are, in 
 some cases, simple earthen works ; in others, they are revetted ; 
 and in others, casemated, both for the service of artillery and 
 small arms. 
 
 IOC.Tknaillon. The term tenaillon, PI. 9, Fig. 81, is ap- 
 plied to a kind of face cover, or conntergnard, r l\ of the demi- 
 lune. It is only to be met with in some of the old fortified 
 places of Europe, ami was added to give more strength to the 
 fronts where the demilune was too small. 
 
 197...IIokn\\okk. The hornwork, PI. 9, Fig. 82, usually 
 consists of a hastioned front, II, with the ordinary outworks, 
 having two long branches, F I\ or wings, which rest upon two 
 adjacent bastions, or two adjacent demilunes, D IJ, of the en- 
 ceinte — its covered-way forming, with that of the enceinte, a 
 
OUTWORKS AND DETACHED WORKS. 77 
 
 continuous line of communication. The object of this outwork 
 is to strengthen a salient or other weak portion of the enceinte 
 
 198...Ck<>\v\-\vork. The crown-work, PI. 9, Fig. 83, con- 
 sists of two or more bastioncd fronts, C, with their outworks, 
 placed in front of Borne portion of the enceinte, to give it addi- 
 tional strength. It is terminated, like the hornwork, by two 
 wings, F F, which rest either ffpon the enceinte, or upon the 
 demilunes, D D. Its covered-way, like that of the hornwork, 
 forms a continuous communication with that of the enceinte. 
 
 19 9... Detached Works. There are two other classes of ex- 
 terior defences besides the outworks, termed detached works 
 and advema d uwk»„ the object of which is either to strengthen 
 some weak portion of the enceinte or to occupy positions 
 which would be of advantage to an assailant in his attacks on 
 the enceinte. 
 
 300... Detached works are such as are placed beyond the 
 covered-way of the enceinte, but within the range and support 
 of its lire. Advanced works are such as, from their advanced 
 ion. receiving but little or no support from the fire of the 
 enceinte, must rely Upon their own resources for defence. 
 The former class are usually open in the rear, so their interior 
 may be exposed to the fire of the enceinte ; whilst the latter 
 should be closed throughout and of sufficient strength of pro- 
 lile to secure them from an open assault. 
 
 201...In PI. 9. Fig. si. is a detached work, /..flanked by 
 the demilunes, I>. of the enceinte. The plan of this work tea 
 lunette, with its covered-way and places of arms, R and &. 
 
7^ INTKRIOR RETRf.XCHMKXT^. 
 
 INTERIOR RETRENCHMENTS. 
 
 202. ..Besides the works exterior to the enceinte, the object 
 of which is to retard the assailant in his attempts to enter it 
 by breaching 1 , engineers have placed within it other works 
 
 which, in some cases, are designed simply to enable the gar- 
 rison to make an effectual defence of the breach, when the 
 assault upon it is made, and give them a secure point of re- 
 treat and safety when driven from it ; and in others, these 
 interior works arc chiefly designed to bring a plunging lire to 
 bear on the assailant's siege works exterior to the enceinte. 
 The former class, intended for the defence of the breach alone, 
 arc termed interior retrenchments I and the latter, awdlierf. 
 
 ^0-°.... Interior retrenchments are either placed within the 
 bastions, -which are the parts of the enceinte usually breached, 
 or in rear of their gorges. Those which are placed within the 
 bastions extend across them, either between the faces or be- 
 tween the flanks. When placed at the gorge, they connect 
 the two adjacent curtains. 
 
 204.. .The plan of these works varies with their position, the 
 size of the bastions, or the more or less of openness of their 
 salient angles. 
 
 205. ..In small bastions with acute salients, when the re- 
 trenchment rests upon the faces, it usually receives the form 
 of a tenaille or inverted redan, the angle of the tenaille being 
 about 100°. When the bastions are large and the salient 
 angle quite open or obtuse, the retrenchment may receive the 
 form of a small bastioned front, PI. 9, Fig. 85, resting upon 
 the faces. 
 
 206. ..Either of these forms may, in like manner, be used, 
 
BASTIONED SYSTEM. 79 
 
 when the retrenchment rests upon the flanks of the bastion. 
 But as this position enables a retrenchment of the form of an 
 ordinary redan to hare its ditches swept by the fire of the 
 flanks of the adjacent bastions, this form is in some cases used 
 in preference. 
 
 207... When placed between two curtains at the gorge of a 
 bastion, the plan of the entrenchment is always a bastioned 
 front. 
 
 20S... Cavaliers are placed either upon the curtains or within 
 the bastions. The latter is the more usual position selected 
 for them. Their plan in this position is usually that of a 
 lunette, the faces and flanks of which are parallel to those of 
 the enveloping bastion. Cavaliers receive a considerable com- 
 mand over the parapet of the enceinte, and in some cases, 
 they are arranged with a tier of casemated fire, above which 
 is an open battery. 
 
 209. ..Interior retrenchments are usually constructed with a 
 revetted scarp and counterscarp, to secure them from an open 
 assault; and, in some cases, a covered-way, with a small reen- 
 tering place of arms, fi, PI. 9, Fig. 85, closed by traverses, is 
 arranged in advance of the ditch, to insure the safe retreat of 
 the garrison when driven from the breach. 
 
 BASTIONED SYSTEM. 
 
 HO.. .A bastioned enceinte consists ofs of bastions 
 
 which occupy the salient angles <>f the polygon, within which 
 the enceinte is enclosed; the thinks of the bastions being 
 usually connected by straight curtains. 
 
 211. ..The sides of the polygon which connect the salienl 
 
 
 
BO i;.wil"NU» BYB1 : 
 
 angles of the bastions, are termed the anterior sides, in contra* 
 <li.-tiiicti.in to the sides of an interior polygon, which, being 
 parallel to tin* first ami occupying the positions of the curtains, 
 arc termed the interior sides. 
 
 212...The l»a>ti<incil enceinte, when its relict' and plan are 
 suitably arranged, possesses the advantage of having its 
 ditches thoroughly swept from within the enceinte itself, 
 thus securing the flanking arrangement of the scarp, whilst 
 the garrison also is kept within the enceinte under the imme- 
 diate eye and orders of their commander, up to the moment of 
 the fall bf the work ; of bringing a cross and Hank fire to bear 
 upon the approaches on the BalientS of the enceinte in the di- 
 rections of the capitals of the bastions: and furnishing a 
 strong direct and cross tire upon the site in advance of the 
 curtains and the faces of the bastions. 
 
 213.. .The principal objections urged against the bastione,d 
 kem arc, that its chief characteristic — a perfect flanking 
 disposition for the entire line of the scarp — is attainable only 
 under certain relations between the requisite relief for a per- 
 manent Work and the length of the exterior side and curtain, 
 which, therefore, restricts it in its application to fortification 
 of a permanent character; that, in order to secure sufficient 
 length of Hank for an effective thinking disposition, the angle 
 between the face of the bastion and the exterior side, termed 
 the diminished angle of the polygon, has to be made so great 
 as to decrease considerably the space enclosed within the poly- 
 gon, whilst the development of the line of the enceinte is 
 -really increased by it; that this direction, necessarily given 
 to the faces from this cause, throws their prolongations in po- 
 sitions very favorable to the erection of enfilading batteries 
 against them ; that the flanks, upon which the whole system is 
 based, lie in positions in which, like the faces, they can be not 
 only ea>ily enfiladed, but are further exposed to a reverse tire 
 from shot which may pass over the parapet of the faces as well 
 ab the opposite flank ; and that these objections are the stronger 
 
 
vaui:anV first method. 81 
 
 as tlic salient angles of the polygon are smaller. 0T as tlio nuni- 
 ber of sides is decreased. 
 
 214.. .Besides these objections, •which, to a certain extent, arc 
 well founded, where the defensive arrangements arc chiefly 
 open, as is the case in most land fronts, others have been 
 urged against this system, which, being rather of a compara- 
 tive character, a- showing the. advantages of other systems 
 <>ver this, will besl l»e examined elsewhere. 
 
 215. ..As the plan and relief of the hastioned enceinte, em- 
 ployed among engineers of the present day, differ in no very 
 material points from those Adopted about the period of Van- 
 han, when the art of fort iti eat ion assumed somewhat less of 
 mere mechanical routine, it has hecome the practice in mili- 
 tary schools in Europe to deduce, from the description of the 
 bastioned method of Vauban ami his immediate snccessoTS, 
 the principles upon which the tonus and dimensions, both of 
 the enceinte and its outworks, as well as their defensive rela- 
 tions, are based. As this course has the farther advantage of 
 exhibiting the views of men who are still looked to as the safest 
 authorities in the art, whilst it gives, at the same time, a his- 
 tory of it- progress and changes from the period when it may 
 he said to have first broken loose from the trammels of mere 
 routine up to the present day, it has heeii also adopted as the 
 ha>is of the instruction given on this subject in this institution. 
 
 V.W HAYS FIRST METHOD. 
 
 216.. .Vauban 1 - of three different methods 
 
 in the places planned by him. The Fortress of V 
 fortified after his third method; | Landau and l;< 
 
 11 
 
Eft) v.u BAJj'fl PTB8T VETHOD. 
 
 alter his second: but the greater pari of the places fortified by 
 him are planned according to his first, or earliest method. . 
 
 L'17...N-.ii:. In the following description of the methods Of 
 Vauban, Oormontaingne and some other French authors, the 
 English yard has been substituted for the French Jni{f toi* 
 
 and the )mir<\ each of which is so nearly the equivalent of the 
 vard as not to affect in any sensible manner the principles Of 
 the defensive relations of the parts. In like manner the 
 English foot lias been substituted for the French toot. 
 
 L'l>...ri;.>Mi.i; <>i- Knckimi:. In the profile of this method, 
 Fig. 1, PI. 1, the scar]) Mall is 3<i feet high, its slope beingfive 
 perpendicular to. one of base; surmounting this is another wall 
 from 4 to t! feet high, the object of which is to sustain the ex- 
 terior of the parapet. The parapet is 18 feet thick, the 
 superior slope being 1-9; the interior crest is 8 feet above the 
 terreplein, which is 42 feet in width. The mean command of 
 the interior crest above the site is about 26 feet. The bottom 
 of the ditch is about 17£ feet below the site. 
 
 2i; , ...I > i..\.\ of Knckixti:. Vauban adopted no arbitrary or 
 invariable combination of parts in his methods. His greal ex- 
 cellence as an engineer is shown in the acknowledged skill 
 with which he adapted the fortifications he planned to the de- 
 fensive requirements of the sites. Selecting long, medium, or 
 short exterior side.-, and varying the lengths and directions of 
 the faces and flanks so as to procure the best command over 
 the exterior ground, and to withdraw these parts from the en- 
 filading views of the assailant. In his works, however, he has 
 generally taken 360 yards as the greatest limit of the exterior 
 side; the perpendicular of the front £ when the polygon is a 
 square; 1-7 for the pentagon; and 1-6 for all higher polygons. 
 With thes» starting points he procured diminished angles 
 which eave more than 00° to the salient angles of the bastions 
 in all cases, and thinks of suitable length both to flank the 
 main ditch and to encounter with advantage the counter-bat- 
 teries which could be erected against them. The following- 
 constructions, both for the enceinte and outworks, are taken 
 
yatban's FIRST MKTIIOl). 83 
 
 from the best French authorities as adopted by hltn for poly* 
 gens higher than the pentagon. 
 
 220...In the plan or t/togd, Pig. 2, PL 1, the magistral is 
 taken as the directing line; the exterior side is 860 yards; on 
 the perpendicular of the Front a distance of 1-6 the exterior side 
 is set off; lines drawn through this point and the extremities 
 of the exterior side, determine the directions of the faces and 
 the lines of defence ; from the salients a distance equal to 8-7 
 of the exterior side is set oft*, which gives the lengths of the 
 faces and the positions of the shoulder angles; the flank \% 
 drawn by taking the opposite shoulder angle as a centre; and 
 with a radius equal to the distance betweeri the shoulder 
 angles, describing an arc to intersect the line of defence, the 
 chord oi this arc is the flank; the curtain is drawn by joining 
 the extremities of the flanks. By this construction the flanks 
 will be about 54 yards; the curtain, 14<i; and the lines of de- 
 fence. 267 — the length of these; being determined so that the 
 salients of the bastions can he defended with the rampart yun, 
 or wall-pi 
 
 L'-Jl...Ti.\ \iua-:. In many of the places constructed before 
 Vauban's time there was a low work, enveloping the enceinte 
 and connected with it, called a faueeo-braie. This work, 
 which had many defects, was suppressed by Vauban, who was 
 the first to use the tenaille in its place. The tenaille has 
 many valuable properties: it covers the arched communica- 
 tion, or postern, under the curtain : masks the masonry of the 
 curtain and flanks, so that a breach cannot lie made, in them, 
 and in this way prevents retrenchments, resting against tl 
 parts, from being turned; a place of arms is formed betv 
 it and the curtain, where troops can be assembled for BOl 
 in the ditches; finally, its Are sweeps the ditch and counter* 
 p, and helps to cover the retreat of troops from the other 
 outworks. The tenaille is separated from the curtain by l 
 ditch 10 yards wiae, and from the thuds- by ditch 
 The form of the tenaille, as Deed by Vauban, w ible: 
 
 in .- made it with a curtain and two small fla 
 
84 v.ur,\N - - I \\:<T Minion. 
 
 parallel to those of the enceinte; in others, it consisted simply 
 of two wings placed on the prolongations of the faces; and, 
 finally, he gave it the form in I'iir. 2, with a small curtain 
 and two wings, which is the one at presenl most generally 
 adopted. The relief of the tenaille i> bo arranged as not to 
 mask t lie fire of the flanks on the ditch of the enceinte 
 along the faces; for this purpose Yaul>an places its interior 
 crest on a leva] with the site, or a Little below it. 
 
 222...]&un Ditch. Vauban followed no invariable rule in 
 Regulating the dimensions of the enceinte ditch ; its most usual 
 width at the salients of tin- bastions, where the counterscarp is 
 an arc of a circle, is about "><> yards ; the rest of the counter* 
 scarp is tangent to this arc, and directed upon the opposite 
 shoulder angles. 
 
 223...Di:mili m: am> Redtjtt. Vauban increased the dimen- 
 sions of the demilune which had been used previous to his 
 time. The object of this work is to secure the gates of the 
 place from a surprise ; to mask from the enemy's batteries the 
 flanks and curtain of the enceinte; and give cross fires on the 
 salients of the bastions. The plan and dimensions of the 
 demilune vary also in Vaiiban's works. It> magistral is gene- 
 rally laid out by taking a point on the bastion face at LO yards 
 from the shoulder angle, and drawing a line from this point to 
 the perpendicular of the front, so as make the face of the 
 demilune equal to 2-7 of the exterior side. The parapet of 
 the demilune is the same as that of the enceinte ; its command 
 feet Less than that of the enceinte. All the outworks in 
 tlii,- system are commanded by the enceinte; the outworks 
 most advanced being also commanded 1>£ those in rear. 
 
 224...To strengthen the demilune, and secure for the troops 
 entrusted with its defence a safe retreat when it is carried, 
 Vauban placed in it a small redoubt. This work, in some in- 
 stances, was only a simple <-r< not* d waU y with a ditch in front ; 
 sometimes it was made of earth, and after tne commencement 
 of thi' siege. 
 
 L'25...The ditch of the demilune is generally about 24 yards 
 
vauban's first method. 85 
 
 wide, and of the same depth as that of the enceinte; its coun- 
 terscarp and that of the enceinte forming a continuous wall. 
 
 226...Covebed-way. The covered-way envelops the entire 
 counterscarp. Vauban placed a high value on this Work, 
 which, to use his own words, " Costs less to the defence and 
 mote to the assailant than any other work." The covered-way 
 prevents all access to the ditch, by a strong fire of musketry, 
 which sweeps all tiie exterior ground ; it is a secure position, 
 where tnx.ps can be assembled in safety for sorties; it covers 
 the retreat of troops from the exterior into the other works. 
 The general width of the covered-way is 12 yards. To set out 
 the reentering place of arms, two points are taken at 20 yards 
 fn.ni the reentering angle, made by the interior crests of the 
 covered-ways of the demilune and bastion, and upon tl 
 crests, and from these points as centres, with radii of 21 yards. 
 arcs are described ; the point of their intersections being joined 
 with their centres, gives the crests of the reentering place of 
 arms. The parapet of the covered-way is terminated in a 
 glacis, the foot of which is from 40 to :,n yards from the inte- 
 rior crest 
 
 L'l'7...Ti: wi B8E8. To close the place of arm.-, and enable the 
 troops to defend the covered-way foot by foot, trav 
 earth formed into parapets are placed at the places of arms. 
 Defiles ory • I ■ • are left between the traverses and 
 
 the crest of the covered-way, for the circulation of the troops* 
 
 The covered-way is palisaded to prevenl surprise. 
 
 228.. .Communications. The oommimieaUons constitute an 
 important part of every system. In Vauban's front, ramps 
 are mad< end from the plane of Bight to the fc rreplein, 
 
 A postern is made under the curtain, to communicate from the 
 interior with the ditch; another postern is made under the 
 
 tenaille. to lead to the demilune ; a doubl .which 
 
 i^ a by a parapet terminated in a 
 
 glacis toward the ditch, nmunication through 
 
 the ditch to the gorge of the demilun . are 
 
 placed in the ditch of the demilune, and cover th< ryin 
 
86 vaiuan'- RB81 mi in-. n. 
 
 the enemy's fire through its ditch : stairs are placed :it the 
 gorges of the tenaille and demilune, and along the counter* 
 p at the places of arms, to ascend from the ditch to the 
 berrepleins oi those works. To communicate with the exte- 
 rior, narrow openings are made in the faces of the reentering 
 place of arms, to lead from the terreplems to the glacis; they 
 are termed soriu passages, or sally-ports, and arc closed by 
 barriers. 
 
 IIKMAKKS. 
 
 229... Enceinte. In the trage adopted by Vauban for the 
 enceinte, it may be observed that the Length and positions of 
 the lines of the front resulting from it are in good defensive 
 relations, both for cannon and small arms. 
 
 230...In the lirst place, the foot of the scarp, throughout the 
 Length of the curtain and the bastions, is thoroughly expos 1 
 to the lire of the flanks, which^ from the diminished angle as- 
 sumed in the hexagon and higher polygons, which [s about 
 L8^°, and the curtain angle, which is nearly 100° — can sweep 
 both the curtain scarp and that of the bastion lace from an 
 embrasure placed at die curtain angle. 
 
 231. ..In the second place, the length of the flank is sufficient 
 to contain as many cannon, at least, as the assailant can place 
 to counter-batter the flank from the glacis crest opposite the 
 flank ; and the flank can also bring an efficient lire of small 
 arms to hear on this battery of the assailant. 
 
 232...The bastions are of good Bize, and would admit of effi- 
 cient interior retrenchments being thrown up in them, although 
 Vauban does not indicate this auxiliary means in his 1st 
 Mi thod. 
 
 238...T) naii.i.k. Vauban substituted the tenaille for the 
 fau8S6-braie, as this latter work facilitated an escalade, and, 
 moreover, exposed the troops in it to the annoyance of the 
 splinters from the walls behind, when exposed to the assail- 
 ant's lire. The tenaille was devised mainly to mask the scarp 
 wall of the curtain and Hanks, whilst its relief was so regulated 
 
v.\r i:\.\V REST METHOD. s 7 
 
 as not to intercept the fire of the flanks oa the enceinte ditch 
 before the bastion faces. The plan of the earlier* tenaillea con- 
 sisted of two flanks connected by a curtain, which were paral- 
 lel to the same lines of the enceinte Tliis form was subse- 
 quently abandoned, as the flanks were found to be exposed to 
 both an enfilading and reverse fire from the assailant's positions 
 in front of the enceinte; and the one now in most general USS, 
 consisting either of two wings Bimply, or of two wings con- 
 nected by a short curtain, adopted in its place. 
 
 The tenaille, however, only partially subserves its object, as 
 it does not cover the entire height of the scarp of the enceinte 
 curtain and flanks; and, what is a more serious defect, it 
 leaves the entire height of scarp of thai portion of the curtain 
 opposite to the ditch, between the tenaille and the bastion 
 flank, entirely exposed from the same position, and liable to be 
 breached. 
 
 'J- }...lh Mii.rxi:. From the small size of this work, it irives 
 hut little cover to any portion of the enceinte except the cur- 
 tain. It is not sufficiently thrown to the front to give a good 
 volume of cross fire on the glacis in advance of the bastion 
 salients; and the reentering formed at this point, by the two 
 adjacent demilune.-. i.». from the same cans', shallow, and of 
 hut little strength. Owing to this last defect, the assailant can 
 easily breach and storm the enceinte at the same time as the 
 demilune. 
 
 Besides these defects, the demilune is not provided with a 
 permanent reduit — a work necessary to enable the demilune 
 to make a vigorous defence, by the support it affords the as- 
 sailed. 
 
 1 bed-way. From the width given to the demiln 
 ditch, the covered-** lanf reverse tire. 
 
 from which they are hut badly screened by the trav< i 
 Their command over the site - too little. Their main 
 
 defect, ; n to the n enterii 
 
 this important position 
 
 **VJ 
 
88 VAUBA2T8 THIRD METHOD. 
 
 mbling troops far Borties by b permanent rddnit, by which 
 any open attack of the covered-way could be prevented. 
 
 236...Dm 1:1 b. The dimensions given both the enceinte and 
 demilune ditches present a formidable obstacle to an open 
 assault, ami render the assailant's passage of the ditch by the 
 more difficult. Tin- demilune ditch, however, offers a 
 wide opening, through which the scarp of the bastion face can 
 be Been down to it,- fool from the assailant's batteries on the 
 glacis crost in the prolongation of the demilune ditch. 
 
 •_'.".7...C"MMr.\i< ations. The communications within the en- 
 ceinte, and from it to the main ditch, are sufficient and con- 
 venient forthe character of the defence designed. Those of 
 the outworks are for the most part narrow, inconvenient and 
 badly screened from the assailant's tire, and. therefore, do not 
 furnish a good provision for an active defence beyond the 
 enceinte. 
 
 238.. .Profiles. The great command over the site, and 'the 
 high relief given to the enceinte, are very much in favor of the 
 defence, both as to' the effect of the fire on the assailant's ap- 
 proaches, and for security against an escalade. But) in attain- 
 ing these objects, Vanban has left exposed to the assailant's 
 distant lire a considerable portion of the scarp wall, which, 
 being destroyed, would lay the enceinte open to a surprise. 
 
 VAUBAiYS THIRD METHOD. 
 
 239...In his 3d Method, PI. H, which differs from his 2d 
 only in some; minor mollifications, Vanhan adopted what may 
 he termed a double enceinte, the interior one being continuous, 
 
 and consisting of small easemated hastioned towers, X, A', 0, 
 
vat • p. ax's third method. 
 
 placed at the angles of the polygon, which are connected by 
 curtains, /', Z, IF, IP, in the form of bastioned fronts, the 
 flanks of which are also casemated, and intruded, with those 
 of the towers, to sweep the ditch of this enceinte. 
 
 240...The second, or exterior enceinte, is not continuous, but 
 consists of large bastions, A, II, K, or oounterguards with 
 flanks, which cover the towers and the faces of the bastioned 
 curtain between them, and of a tenaille, which lies between 
 the flanks of the counterguards and covers the curtain of the 
 interior enceinte. 
 
 241. ..In advance of this exterior enceinte is placed a demi- 
 lune, arranged with flanks, which contains a small revetted 
 redoubt, and a covered-Wfty similar to the one in his 1st 
 Method. 
 
 •_> I •_'... Pi.w. The lines joining the salients of the counter- 
 guards form the exterior sides, and are taken at 360 yards. 
 Tlie perpendicular, D, is one-sixth of the exterior side, or 
 60 yards. The face. J ff t one-third the exterior side, or 120 
 yards. The flank. // h\ is constructed as in the 1st Method. 
 
 LM.°)...Tlie tenaille Consists simply of two wings in the pro* 
 longation of the faces of the oounterguards; a ditch L0 yards 
 wide is left between the tenaille and the flanks of the counter- 
 guard. Hie gorge line of the tenaille and the flanks of the 
 eonoterguards lie on the line L J/, joining the salients of the 
 towers. 
 
 844...To set out the tower- and connecting curtain, aline, 
 .V '/'. is drawn parallel to I. .)/. and at 16 yards. The fiai 
 //. (j. of the towera are drawn through points /'. at 11 yards 
 from .V. The portion of the flank-. /'. /,'. exterior to the cur- 
 tain, being 12 yards, and the interior portion, /' Q } - 
 The bees are found by joining the points /.. //. 
 
 L'i:>...Tii.' perpendicular, T T\ of the bastioned curtain is 
 1" yards. The flanks, if, FT, are on the prolongation! of the 
 count. Ti/uard flanks. The curtain, W f . ie parallel to /, M. 
 
 ■ ructed l>v de- 
 scribing an arc from < 
 L2 
 
90 VAUBAN's iiiii:i> KBTHOD. 
 
 and drawing a tangent to this arc from the point correspond- 
 in-' to /. on the opposite flank, to Z H . 
 
 249.. .The salient, C\ of the demilune is at 110 yards from 
 the point 0, where a line parallel to the counterguard bee, 
 •and .'in yards from it, cuts the perpendicular of the front. The 
 demilune face, C F' , is 96 yards, and ranges on a poinl />'. at 
 80 yards from the point JET. The flank, F* granges pn a 
 point at 2 yards from the poinl //, and is terminated on the 
 counterscarp of the exterior enceinte, which is drawn front 
 a point j??, at G yards from O, tangent to an arc described 
 from A, with a radius of 30 yards. 
 
 218. ..The salient of the demilune redoubt is at 4(5 yards 
 from the point O. The face of the redoubt is 30 yards, and 
 parallel to that of the demilune; its flank, G' 11', is also par- 
 allel to that of the demilune. 
 
 249. ..The demilune ditch is 20 yards, and that of the redoubt 
 is 12 yards. The general arrangement of the covered-way is 
 the same as in the 1st Method. 
 
 250...Pbofd bs. The profiles of the interior enceinte and of 
 the demilune redoubt are alike, as shown on C D" ; and tlu.se 
 of the COUntergard and demilune are the same as shown ou 
 E" F". 
 
 251.. .The parapets of the towers are of stone, the flanks 
 being pierced with two embrasnres. The flanks of the ease- 
 mates are also pierced for two guns. The centre of the tower 
 is occupied by a stone traverse. The casemated flank Z II'. is 
 pierced for only one gun — all the other defences are open. 
 
 252... Remake. The plan and profiles are referred to a plane 
 of comparison taken -I feel below the horizontal plane of site. 
 The references are in feet and fractional parts of feet. The 
 horizontal distances in yards and feet. 
 
 253. ..The leading idea which seems to have governed Vau- 
 ban in the dispositions of his 2d and 3d Methods, was to make 
 the interior enceinte serve as a general retrenchment with 
 covered defences, which could be brought into play at the 
 moment when an attempt was made to pass the interior ditch 
 
 W 
 
FAUBAn's ninn) METHOD. 91 
 
 either by sap or openly. Besides this prominent feature of the 
 2d and ."-'1 Methods, they are both great improvements on the 
 1st Method, in the greater dimensions given to the counter- 
 guards and demilunes; in the organization of the latter Murk 
 ■frith a permanent though small redoubt, and in the better 
 covet afforded to the masonry of the two enceintes and the 
 outworks, both from the relative position and relief of t! 
 elements. This la>t purpose) however, is but partially effected, 
 for the interior enceinte, which, owing to the small thinks 
 given t<> the demilune (which last have but a slight bearing on 
 the defence, and, therefore, might have been omitted), and the 
 opening between the tenaille and counterguard flanks fan 
 be breached from a position near the reentering place of arms, 
 and thus be exposed to assault at the same time that the breach 
 of the counterguard is attacked. Besides this defect, a great 
 part of the scarp wall of this enceinte in rear of the tenaille. 
 i.> exposed to the enemy's view over the tenaille. as the relief 
 of this wqrk has to be so far reduced that the tire of the cmin- 
 terguard think can be brought to bear on the breach that may 
 be made in the face of the opposite counterguard. 
 
 254...The stone towers are badly contrived, both for strength 
 and defence. The upper platform, surrounded as it is with a 
 Btone parapet, and having a traverse of the same material in 
 the centre, would be a perfect slaughter-house under a h< 
 fire of artillery directed against it. The arches of the c 
 mates are inconveniently placed for the ,.t' the guns, 
 
 and. having the exterior walls for one of their abutim 
 would give way with the destruction of these walls, and bring 
 
 down all the superstructure by then- fall. 
 
 t may !.<■ observed that the in- 
 r enceinte and the couuterguards have the same com- 
 mand, which would be found greatly to the disadva 
 the forti :i ;i~ the enemj has succeed* d in 
 
 "ii of the latt< r. 
 256... The low r< nnterguard and the * 
 
 berm at top, would subj< • oik to be assaulted by 
 
'.••_' BMQN1 'ai.ni.m ;'a M! inoi). 
 
 lade at points along it.- face and flanks at the same tittie that 
 an assault is made on it.- breach : thus paralyzing the action at 
 temporary retrenchments thrown up within this work to pro- 
 tect the breach. 
 
 L'."iT...It was owing, probably, to these obvious defects, and 
 tin- great cost of the baehoned towers, that Corrnontaingne, 
 who, in his writings, professes to follow out the leading ideas 
 of Vauban, selected the main features of his 1st Method 
 rather than those of his 2d and .".d, in the bastioned front 
 which has received his name. Although imperfectly devised, 
 both as to plan and construction, the 3d Method of Yauhan 
 presents more elements of resistance than Cormontaingne'i 
 front; and. with suitable modifications of the interior enceinte 
 and the demilune to remedy the defects which have been 
 pointed out, and by increasing the dimensions of the interior 
 enceinte so as to afford good-sized bastions, with strong flank- 
 ing dispositions, it would oft'er far superior defensive means 
 than it now possesses. 
 
 CORMONTAINGNE'S METHOD. 
 
 258.. .Corrnontaingne, the immediate successor of Yauhan, 
 holds a place only second to this master of the art in the esti- 
 mation 01 the engineers of the French school. Corrnon- 
 taingne. who to superior abilities united a wide range of 
 experience, both in the construction and in the attack of per- 
 manent works, studied with great care the results of Yauban's 
 immense labors. In working out the front which has received 
 his name, Corrnontaingne seems to have applied himself rather 
 to remedy the defects noticeable in the methods of Vauban, 
 than to produce any radical change in the combinations which 
 
COKMoN I AIM.M l'fl METHOD. 
 
 had thus far received the sanction of engineers generally. He 
 was thus led to reject the 1st and 2d Methods of Vauban from 
 the defects which have beeri hotic< d, and also from the in- 
 creased cost of constructing the bastioned towers', and to take 
 the 1st Method as the basis of his own changi 
 
 259...Cormontaingne was the first to develop clearly the in- 
 fluence of large demilunes on the progress of the attack, by 
 their forming deep reenterings between them in front of the 
 bastion salients, and also the increased strength gained by for- 
 tifying on a right line, or on polygons wkh a great number 
 of sides, as in both of tlx the fronts assailed can no: 
 
 enveloped by the assailant's works, and the demilunes from 
 their salient position intercept the prolongations of the bastion 
 faces, and thus mask them from the positions from which alone 
 an enfilading fire could be brought upon them. Besides tliis, 
 Cormontaingne lays down a> a principle, that no masonry shall 
 be exposed to th< distant batteries of ih& assailant; and to 
 obtain this point he has so arranged the height of his principal 
 scarps, and the command given to the glacis crest in front of 
 them, that the top of the scarp shall not lie aboVe the level of 
 this crest, thus masking the entire scarp-, by the earth forming 
 the glacis, from all positions in advance of the glacis crest 
 
 Sis modifications of the plan and profile of Vanbau's 1st 
 Mi thod, chiefly result from the above m a basi 
 
 200.. .Enceinte. Tin- modifications of Vauban's tract 
 4, PI. 1. are different in the various works of Cormontaing 
 hut the following he indicates in his m< tnoirs as the most 
 feet T >r side i.^ 860 yard.-: the perpendicular 
 
 the face- of the 1' of the exterior side; the flanks . 
 
 4'» yard.-, and are -.. placed that the curtain shall he 1 i'm yai 
 this combination makes the Lines of defence somewhat l< 
 and the ha.-' ewhat -mailer, than in Vauba thod. 
 
 261. ..The dimensions <>t' the enceinte ditch ai rnlated 
 
 h\ Cormontaingn< earth sufficient for the em- 
 
 bankmei ilient, and IV 
 
'.'1 OORMOXTAIM.M ."> MITIIOD. 
 
 4 yards wider opposite the tenaille; this admits the entire fire 
 of tin- flanks to sweep the ditch. 
 
 262...Texaille. The tenaille is made with a curtain and 
 wings; a ditch LO yards wide being left between It, the cur- 
 tain and the flanks. 
 
 l'i;::...I )i mil ink. Corniontaingne placed little value on 
 small demilunes, as they form l»ut slight and, therefore, weak 
 reenterings before the bastions, and, consequently, retard but 
 little the enemy's attack upon the bastions; besides thi 
 small demilune covers but very imperfectly the shoulder 
 angles of the bastions. To remedy these defects, his demilune 
 is so laid out that the prolongations of the magistrals of its 
 faces will intersect the ba.-tioii faces at 80 yards from the 
 Bhoulder angles; the lengths of its faces being L30 yards. 
 
 •j<;4...By thus enlarging the demilune, sufficient space is 
 gained to place a strong redoubt in its interior. The defence 
 of the demilune may be made with more obstinacy, from the 
 Bupport it receives from the redoubt; and the enemy will be 
 obliged to carry the redoubt before he can assaull the in-each 
 lie may have made in the bastion face, as this breach is see* 
 in reverse by the fire of the flanks of the redoubt. 
 
 £65. ..Demilune Reduit. To circumscribe as much as prac- 
 ticable the space in the demilune which the enemy, after he 
 gains it, requires for his works, the extremity of the demilune 
 terreplein, which is also the top of the counterscarp of the, re- 
 doubt, is drawn at 20 yards from the magistral of the face; 
 tin' ditch qf the reddidit is 10 yards wide, and the magistral 
 of its face is parallel with the counterscarp. By this arrange- 
 ment the ditch of the redoubl is well flanked by the face of 
 the bastion near the shoulder angle. To lay out the Hanks of 
 the redoubt, the counterscarps of the enceinte are prolonged 
 to intersect the perpendicular of the front; from this point of 
 intersection a distance of 20 yards is set oil' along each coun- 
 terscarp, the two points thus obtained arc joined by a right 
 line, which is the gorge of the redoubt; from the extremities 
 of the gorge two lines are drawn parallel to the capital of the 
 
cormontaim.xk's method. 95 
 
 demilune, those linos limit the torreploin of Ihc flanks; the 
 magistrals of the flanks arc drawn parallel to and at in' yards 
 from the last lines. The ditch of the demilune is 20 yards 
 wide; its depth is the same as that of the enceinte. 
 
 2(J6...Cov] Ri o-way, bto. The general width of the eovered- 
 way 1 is 10 yards. Cormontaingue enlarged considerably the 
 reentering place of arms, to which he added a redoubt with a 
 revetted scarp and counterscarp. The addition of this redoubt 
 la a great improvement upon the covered-way of Vauban, who 
 indicates in his works small redoubts of earth, or tambours of 
 wood, for the same purpose. Cormontaingne'a redoubt in- 
 creases the Btrength of the covered-wayj the troopd assembled 
 in the covered-way, for sorties, are Becure under its fires: it 
 6oos in reverse, and protects any breach made in the face of 
 the demilune; finally, it serves, in connection with the ex- 
 tremity of the demilune, to cover the opening left between the 
 flank.- of tlie baatioe and the wings of the teuaille, through 
 which, if a breach was made in the curtain, the interior re- 
 trenchments, resting upon either the flanks or face.- of the bas- 
 tion, could he turned. 
 
 •J|>7...To lay out the interior crests of the reentering place of 
 urns, two points .-ire taken on the counterscarps of the bastion 
 and demilune, at 54 yards from their point of intersection; 
 
 from these point- a- c Qtres, with radii of 60 yard-, arcs are 
 
 ribed, whose in* , joined with the centn 
 
 the direction of the face-. The magistral of it> redoul I 
 found by a similar construction j distances of J" yards being 
 off along the counterscarps, and the faces being drawn 
 from these point- bo :i- to be 86 yards long. The ditch of the 
 redoubt i.- 5 yards wide and 2\ yards deep. 
 
 268„.Tj are placed along the covered-way,- to d 
 
 the places of arms, defend th< i-way. and intercept pro- 
 
 fircd in ri 
 269...The i 
 line, to allow room iW th< - of the • ' I " I n • short 
 
 bran throw a lire on the salient 
 
96 i:M"M \in.;\i."> mi :i hod. 
 
 covered-way; ihe positions of the long branches are bo taken 
 that the defiles may be seen and Bwept by the liiv of the 
 works in their rear, 
 
 270... Profiles. Cormontaingne, after a series of trials, whose 
 •t was to give the ditohes such dimensions that they should 
 I'lirn i>li the earth required for the embankments, regulated the 
 command of the different works as follows: The lowest work, 
 which is the demilune covered-way, he lavs down as a rule, 
 shall command the exterior ground by not less than 7 A feel ; 
 and the works most advanced shall be commanded by those 
 in their rear. 
 
 ■_'7l... It was found that, for the purpose of equalising the 
 excavations ami embankments of tin- front, the crest of the 
 demilune covered-Way should have a command of 1<»A feet 
 above the natural ground. The crest of the bastion covered-; 
 way, ami of the reentering place of arms, command the crest 
 of the demilune covered-way by 2 feet. The magistral of the 
 enceinte is horizontal, its elevation being the same as the 
 mean elevation of the crest of the bastion covered-way. The 
 salient of the bastion commands its covered-way by 8 feet 
 The total height of the scarp is 30 feet. This dimension has 
 since been generally adopted by engineers— a wall of this 
 height opposing a sufficient obstacle to an attempt at escalade, 
 The absolute relief of the flanks is thus made 37-J feet ; with 
 
 this relief a piece, firing under a depression of l-(> through an 
 embrasure in the Hank, and in the direction of the curtain, 
 will strike the bottom of the ditch at the middle point of the 
 Curtain; BO that were the relief increased, the length of cur- 
 lain remaining the same, the ditch would no longer be thor- 
 oughly flanked. 
 
 272..,Thfl relief of the tenaille is determined as in Yauban's 
 Method, so as not to mask the lire of the flanks upon the ditch 
 opposite the extremity of the demilune, as it is here that a 
 breach may be made in the bastion i'aee through the ditch of 
 the demilune. 
 
 273...The demilune is commanded by the enceinte, 3 feet, 
 
COKMo.NTAIM.NkV Ml I'lIOD. !»7 
 
 and by its own redoubt, H feel ; the demilune, therefore, com- 
 mands its covered-way, 7 feet, which is more than La indispens- 
 ably requisite; for ;m enemy, standing on the crest of the 
 covered-way") cannot hare a plunging fire into a work in the 
 rear of it it' the latter commands the cresl by 5 feet. 
 
 274..,The redoubt of the reentering olace of arms commands 
 the crest of the glacis only 4$ feet; its interior caesl 
 placed as not to mask the tire of the bastion faces on the 
 glacis in advance of it. 
 
 875... Hie interior crests of all the works are 7£ feet above 
 their terreplein, except that of the tenaille, which is *»-£ 
 feet, and of the redoubt oftlie reentering placeof arms, which 
 i.- !' feet. The interior crests of the faces of all the work- 
 posed t<» enfilading tires are one foot higher at the salients 
 than at the extremities. 
 
 27n\..The profile of the parapet of the principal outwork 
 -.line as that of the enceinte. 
 
 L'77...(.'oMMt-.\-i< \iio\>. The communications are generally 
 of the same nature, and placed about in the same positions, as 
 in Vanban'fl Method. 
 
 l'7 v ...<.] u i-. The planes of the glacis are bo determined 
 that they may be swept by the lire of the works in the rear : 
 their inclination is usually about twenty-four base to one alti- 
 tude. 
 
 879...Interioh Retbenobxentb. Oormontsingne indict 
 
 the gorge and ghouldeN of the ha-thm as the position for an 
 
 interim- retrenchment, when this addition to the front is made 
 solely with a view of disputing the breach in the bastion and 
 its interior with the assailant. In this CM 
 treiichment the form of a tenaille. or a bastioned front, 
 
 her upon the shoulder angles of the bastion, or npon the 
 
 two adjacent curtain.-, on points beyond the pro 
 
 ditch between the tenaiiles and the flanks, and in tl 
 it tin- form d front. 
 
 In the form . the port 
 
 nee, but • 
 13 
 
: |V < OBMOCT Ai.Ni.M ;'a Million. 
 
 trenchment is liable to be turned, by a breach made in the 
 Hank. <.r in the portion of the curtain where it joins the flank. 
 In the latter ease, a breach in the bastion places the whole of 
 the interior within view of the assailant, bnt the retrenchment 
 itself is secure from its position from being turned, as a breach 
 in tin- curtain cannot In- made in rear <>t' it. 
 
 280.. .< \\ .\ i ii BR, When a greater command of the site than 
 that afforded by the enceinte is requisite on any front. Cor- 
 montaingne places a cavalier within the bastion. To this work 
 he gives the same form ;is thai of the bastion, placing the faces 
 ami flanks of the two parallel to each other. The faces of the 
 cavalier arc alone revetted, as well as the counterscarp of 
 their ditch which is cut within the bastion. This ditch is 
 broken off at the shoulder angles <>t the cavalier ami directed 
 upon the faces, these portions also bavin-- a revetted scarp and 
 counterscarp. A parapet is thrown up behind the scarp and 
 between the flank of the cavalier and the bastion faces, thus 
 isolating the anterior portion of the bastion, and furnishing an 
 interior retrenchment which, when the shoulders and flanks of 
 the bastions are masked from the assailant's view, can only be 
 carried by a breach made either in the cavalier face or in the 
 portions resting on the cavalier and bastion faces. 
 
 • 281...Kkmai;ks. From the preceding description, it appears 
 that the most important modification made by Cormontaingne, 
 in Vauban's 1st Method, consists in the means taken to cover 
 the masonnj from distant, batteries; capacious bastions, sus- 
 ceptible of receiving efficient permanent interior retrench- 
 ments; an enlarged demilune, which places the bastions in 
 strong refinterings, covers the shoulder angles, and admits of 
 a redoubt in its interior, which work strengthens the demilune, 
 and sees in reverse the breach made in the bastion face; an 
 enlarged reentering place of arms, containing a redoubt, which 
 strengthens the entire covered-way, and covers the movement 
 of the troops in sorties. 
 
 282.. .These modifications, although of great value, and con- 
 stituting an important step in the art, still leave much to be 
 
 M 
 
METHODS OF THE SCHOOLS OF M K/.IKKKs WD METZ. 99 
 
 desired ; and engineers, since Cormontaingne's time, have 
 BOtlght to remedy the detects of his method, of which the fol- 
 lowing arc the principal. The enceinte lias rather too slight 
 a command, and it is without any bomb-proof shelters ; the 
 inclination of the superior slope of its parapet, which is 1-9, 
 is too small to have the ditches well flanked ; a breach can be 
 made in the bastion face through the ditch of the demilune; 
 there are dead spaces in the ditch of the demilune near 
 the extremities of its faces; the redoubt of the reentering 
 place of arms is not tenable after the demilune is taken ; the 
 traverses of the covered-way do not afford the requisite pro- 
 tection to thai work ; finally, communications are mostly in- 
 convenient, and not well covered from the assailant's fires. 
 
 METHODS OF THE SCHOOLS OF .1IEZIERES AND METZ. 
 
 L' v ."....The School of Application tor engineer and artillery 
 officers, first established at tfezieres-and subsequently at M<u. 
 has given to France, from about the period of the French 
 R volution down to the presenl day, the far greater portion of 
 the many able officen who have gained such universal and 
 red celebrity for these two corps. 
 
 L'M...In these schools the precept! of Vauban and Cormon- 
 taingne have been jealously guarded ;J s the highest authority, 
 and their manuscript* and published works have formed the 
 of the instruction given in them. 
 
 2s. - lit modifications were proposed in theft 
 
 of Cormontaingne by two ' 
 
100 METHODS OF THE SCHOOLS OF MUlflUS \M> MKTZ. 
 
 and taught by them in the course of permanent fortification 
 given in the school. These changes chiefly consisted in en- 
 larging the demilune and making it more ,-alient; and in 
 placing in the flanks of its redonbl casemates for cannon, with 
 reverse views on the breaches that might be made in the bas- 
 tion faces. 
 
 280...The teaching of tlu- Bchool of Met/. has received its 
 principal impress from Genera] Noizet, himself a pupil of 
 General Bazo, regarded as the first among the successors of 
 Vauban and Oormontaingne, who, for several years, whilst si 
 captain <»t' engineers, performed the functions of professor of 
 fortification, and who has recently given to the public the re- 
 sults of his lectures delivered in the school. 
 
 28T...The front, which for sonic years hack and up to the 
 present time, has been taught in this school, goes by the ap- 
 pellation of Xoizi /'.* Mi thod. In it there is no sensible depar- 
 ture from the views and methods of Vauban and Oormon- 
 taingne; the object being to introduce such modifications into 
 the front of the latter as would remedy some of its acknowl- 
 edged defects. In doing this, another object was kept in view, 
 which was to present in the combinations of this front a prob- 
 lem, in the solution of which the pupil would be called upon 
 to apply both the elementary principles of fortification and the 
 geometrical methods that the engineer has to use as his princi- 
 pal tool in such problems to a special case, that oi a front 
 adopted to a horiecntai aitd. It is in this point of view that 
 the analysis and construction of this i'ront have been adopted 
 as the basis for the elementary instruction given in permanent 
 fortification in this institution. 
 
 
ntoizet's method. 101 
 
 NOIZET'S METHOD. 
 
 288... General Ki quibbmebts. Noizet, in his front, takes as 
 the basis of the construction of the enceinte, the length of the 
 exterior Bide and the command; assuming these within the 
 limits laid down by Yauban and Cormontaingne; and in the 
 combinations of outworks with the enceinte, following the 
 latter engineer; introducing only Buch modifications as seem 
 t<> beet fulfill the general conditions of the problem,. which are 
 as follows: 
 
 1st. The enceinte must be secure from a surprise by esca- 
 lade: present an unbroken line on every side by which it 
 can be approached by the assailant; and hare its scarp tho- 
 roughly swept by fire from within the enceinte. 
 
 I'd. The parapets of the enceinte and outworks must be 
 proof against projectiles <»f the heaviest calibre. 
 
 I'd. The scarp walls of the enceinte and outworks must be 
 
 masked from all positions that can be taken up by the assail- 
 ant for bis breaching batteries beyond the crt st of the gls 
 
 4th. The flanking dispositions, both of the enceinte and out- 
 work.-, must be adapted bo the range of small arm.-, within 
 irate lira 
 
 i. The command of the enceinte must be so regulated as 
 i erlook all the outworks and bring their interior, their 
 ditches, the glacis and the site beyond it thoroughly under lire 
 of both artillery and BtnaU ai 
 
 i command of the outwork- must 1"' so combii 
 that the more adi shall be commanded by the i 
 
 tired; and, when this cannot 1 d, the retii 
 
 which is commanded by an advai 
 int< 
 
 
 
103 roust's ig raoft 
 
 7th. The outworks must be so combined that they shall tall 
 into the possession of the assailant in succession, from the 
 more advanced to the more retired; and the more important 
 ones should receive a sufficient height of scarp wall to secure 
 them from being entered by a sudden rush of the enemy. 
 
 Bth. There must be a sufficiency of tin' various kinds of 
 communications to admit of a prompt circulation, both within 
 the enceinte ami to the exterior, tor the ordinary service of 
 the garrison and for sorties against the assailant. 
 
 28!»...<ii m SAL Data OF THE Km i intk. In the following de- 
 scription ami analysis of the front of Noizet, the plane of com-i 
 parison is assumed at 60 tot below the horizontal plane of 
 . the reference of which will he, therefore, (60,0). The 
 yard is taken as the unit for the horizontal dimensions of the 
 plan ; and the foot as the unit for the references and vertical 
 dimensions. 
 
 Converting the French measures into their equivalent Eng- 
 lish units, the exterior side of the front is 880 yards; the 
 height of the scarp wall, .'>."> feet ; the command of the interior 
 Crest of the curtain over the plane of site, L'l feet; and its 
 height above the magistral, 13 feet. 
 
 29<i...Pkoj ii. k of Enceinte. PI. 2, Fig. 4. The profile of 
 the enceinte here given is similar to that of Oofmontaingne, 
 and was adopted by subsequent engineers until the more re- 
 cently modified one already described. Its slopes and dimen- 
 sions are as follows: The scarp and counterscarp slopes, 20-1, 
 or one base to twenty altitude. Exterior slope, 1-1, or 15°. 
 Superior slope, l-G. Interior slope, 3-1. Banquette-slope, 4. 
 Rampart-slope, $. Terreplcins S feet helow the interior crests. 
 I'.erin, 2 feet. Distance between the magistral and foot of the 
 exterior slope, L.5 feet. Thickness of parapet, 20 feet Height 
 of interior crest above the banquette-tread, 4.5 feet. Ban- 
 quette-tread, K."> feci. General width of terreplein, estimated 
 from the vertical through the interior crest, 48 feet. 
 
 2DJ...M ai.i.vi Bill OF iin: (Vktain. The length of this is 
 determined by the condition that the artillery fire from the 
 
\ot/.i.t"s mkthod. 103 
 
 .flanks, under the depression of 1-fi, shall attain a point at 1.5 
 feet above the bottom of the ditch, at tin- centre of the cur- 
 tain ; the bottom of the ditch itself, at the centre, being, for 
 r the purposes of drainage, L. 5 feet higher than at the extremi- 
 ties of the curtain, thus giving to the scarp a height of 31.50 
 feet at the centre, instead of 33 feet, the general height 
 throughout the enceinte. 
 
 Supposing, now. a section, PI. -. Figs. 2, 4, to be made 
 through the flanks by a vertical plane passed through the foot of 
 the curtain scarp, and that a line he drawn in it, parallel to the 
 superior slope and at 3 feet below it, to represent the direction 
 of the artillery tire, this line must attain the point at 1.5 feet 
 above the bottom of the ditch, at the centre of the curtain, to 
 fulfill the required condition of a thorough flanking disposition 
 throughout the entire extent of the enceinte. If, then, a hori- 
 zontal line he drawn from the point to lie attained to intei 
 the vertical through the interior crest, it will be the horizontal 
 distance between the interior crest and the centre of the cur- 
 tain, and from the construction, will he equal to six times the 
 perpendicular distance intercepted between it and the line of 
 artillery fire. f 
 
 Now. from the above there i- given to calculate this hase 
 the entire height of the interior crest, above the bottom of 
 the ditch. 44.60 feet : the height of the same point above the 
 line of artillery I t ; and the height of the point to he 
 
 attained above the bottom of the ditch, L. 5 feet. The distance 
 •OUght, then), -re. will he .; H.:,o ft. — UK) ft.,-l'4M ft. 
 
 To obtain the length of the magistral corresponding to this 
 distance, it will only be requi abtract from it the hori- 
 
 zontal distance between the interior crest and the point ot 
 on corresponding to the magistral ot the flank. Thia 
 distance is composed of the thick' the parapet, the 1 
 
 of the exterior slope, and the herm. The first i- 20 feet. 
 
 id is found by taking from the height of theii 
 above the mag stral, which is 13 tb the thick' 
 
 of the para] 
 
Ill4 N"l/.l l""> Ml 1 HOD. 
 
 feet. The third is 1.50 feet. The required distance; therefore*,. 
 
 !,, ft.— il'.i i't. + O.OG ft.+1.50 ft.) = 20S.S4 feet, or 00.(11 
 yards. 
 
 292...Magisteal of Km mmi:. PL 2, Fig. 5. Having found* 
 the Length of the magistral of the curtain, the projection of 
 the- magistral of the enceinte on the plane of reference is de- 
 termined as follows: Draw aline for the exterior Bide, and Bel 
 off on it .1 II :380 yards ; bisect this distance by a perpen- 
 dicular, on which set oif C IJ=l-6 A£=63.33 yards; from A 
 and B draw lines through D, these are the directions of the 
 laces and lines of defence ; draw a parallel to D, on each 
 Bide of it. and at 69.61 yards, the length of the half curtain, from 
 it, join tin' points and // where these parallels intersect the 
 lines A. D and B I) prolonged; G II is the position of the 
 curtain; G IJ and II A the lines of defence; from and // 
 draw a line, making an angle 1-6 with the perpendicular, to 
 the curtain at each of these points; the parts /'/and F II oi 
 these last lines are the thinks, and .L /'.'and B /-'the faces. 
 
 293. ..The position of the magistral with respect t<» the plane 
 of reference, is determined as follows: The magistral of the cur- 
 tain is horizontal. As it is 13 feet below the interior erestj 
 and this line is placed at '21 feet above the plane of site, the 
 magistral is 8 feet above this plane, and, therefore, from the 
 position given the plane of comparison, 6S feet above this last. 
 plane; its reference, therefore, is (68.0). The flank is 1.5 feet 
 lower at the shoulder than at the curtain angle, the reference 
 of the shoulder is. then, (66.50). Tho face is horizontal, and 
 its reference also (66.50). 
 
 294.. .M anm:u OF iil.'i'llJ.MlM.No nil'. POSITION OF A POINT OF mi. 
 Interiob C$S6T, To determine the projection of a point of 
 the interior crest contained in a profile plane, the height of 
 the point above the magistral being known, we first subtract 
 from this height 1-6 the thickness of the parapet, the remainder 
 will be the height of the exterior crest above the magistral, 
 and, when the exterior slope is 1-1, will also be the base of 
 the slope; adding together the thickness of the parapet, the 
 
noizkt's method. 105 
 
 base of the exterior slope as just determined, and the distance 
 from the foot of - the exterior slope to the magistral, the sum 
 will be the horizontal distance between the magistral and inte- 
 rior crest, or the distance to l>e set off, along the trace of the 
 profile plane, from the magistral, to obtain the projection of 
 the required point of the interior crest. 
 
 L'!C>...Ixtki;toi; CbEST Off THE Knminii. PI. 2, Fife H. The 
 position of the interior crest above the magistral is fixed as 
 follows: That of the curtain is parallel to the magistral, and 
 13 feet above it.« Those of the flanks ami faces of the bastion 
 an' contained in the same plane, the scale of declivity of which 
 is taken parallel to the bastion capital. The position of this 
 plane is determined by placing its horizontal, which coincides 
 with a pancoupe* 4..">u yards in length at the bastion salient, at 
 
 4..*><> feet above the horizontal drawn through the points where 
 the flanks join the curtain. 
 
 The reference of the interior crest of the curtain from the 
 above data will, therefore, be ('Sl.(i); and the horizontal dis- 
 tance .,t' any point of it from the magistral 31.16 feet, or 10.38 
 yards, as these two lines are parallel* 
 
 Having drawn the projection of the interior crest of the 
 curtain, the point where it joins the flank may be determined 
 approximately, and with sufficient accuracy, by bisecting the 
 curtain angle of the magistrals, and taking the point, wl 
 the bisecting line cuts the interior civ-t. as the extremity of 
 the flank. From this point, of which the ref 
 if a line be drawn perpendicular to the bastion capital it will 
 be horizontal (81.0) of the plane 1 of the interior a the 
 
 ion : that at the pancoupe is 4..*.<> feel higher, and rta n 
 will, therefore. I To find the position of this 
 
 \uH horizontal, which is also that of the pancoupe, draw ' 
 lines parallel to the bastion capital, and 2.16 yards from it, 
 they will limit the pancoupe'. Now, a- the extremity of tin-. 
 pancoupe* i- a point ..; i 1 .'' i of the bastion fa 
 
 and it.- n te h< ighl of this pou 
 
 stral i> 1'.' feet, as tin 
 14 
 
106 vizi.rV KKHOD. 
 
 The horizontal distance, therefore, from this point to the mag- 
 istral is (90 ft. +15.66 ft. +1^50 l't.) = 37.1(> ft. =12.36 yard* 
 Drawing a parallel, therefore, "to the magistral of the face, ami 
 at L2.38 yards from it, the point where it cuts the parallel to 
 the Capital, a1 2.15 yards from it, will be the required point, 
 tihrough which the horijontal (85.50) is drawn. 
 
 I laving tw<- horizontals of the plane, its Bcale of declivity can 
 be constructed, and other horizontals be detertnined. The pro- 
 jection of the poinl of the interior crest of the face on any givea 
 horizontal, can lie found by the same process as the one jiist 
 described, For example, take the horizontal, (84.0) 5 the per- 
 pendicnlar distance of the point on it from the magistral i> (90 
 ft.+l4.16 ft.-f !.:.<) ft.)=35.06 ft. or 11.88 yds. The two points 
 thus determined being joined, will give the projection of the 
 interior crest of the face. 
 
 To find that of the flank, of which one point, (81.0), lias been 
 found, bisect the shoulder angle of the magistral, the point 
 where the bisecting line cuts the interior crest of the face will 
 give, approximately, the other extremity of the line required* 
 
 The constructions for the interior crests, just given, are only 
 approximations to a true result ; as the horizontal distances 
 calculated, being those contained in profile planes, ought to 
 have been set oft* perpendicular to the projection of the interior 
 crest; but the difference between the results of this approxi- 
 mate method and one rigorously accurate will, in the present 
 case, be so small, owing to the slight divergence between the 
 projections of the magistral and interior crest of tin- face, as 
 not to affect, in any appreciable degree, the real positions of 
 the required points. The same remarks are applicable to the 
 constructions for finding the extremities of the flank. 
 
 29C...1\\kai , kt ok En< i.inii:. Having drawn the interior 
 crest of the enceinte, all the other lines of the parapet — except 
 the foot of the exterior slope. — and the inward line of the terre- 
 ph'in are drawn parallel to it. The foot of the exterior slope 
 is drawn parallel to the magistral. 
 
 Tikkki-i.i.ix of Kxei.iMi. PL 2, Fig. (i. The tcrrcpleins of 
 
noi/i :r's MKTiion. 107 
 
 the faces and flanks are in a plane parallel to that of their in- 
 terior crest and 8 feet below it. estimated vertically. To find 
 the reference of any horizontal of the terreplein, it will be only 
 necessary to subtract 8 feet from the corresponding one of the 
 Interior crests. Tims, (85.50) being ■ reference of a horizontal 
 of the interior crest, that of the terreplein corresponding is 
 (77.:»0). 
 
 The terreplein of the curtain slopes 1 foot from the foot of 
 tin- banquette-slope to its inward line, which places this last 
 line 9 feet below the interior crest. 
 
 297...Kami'.\i.i-m.mi-i; and Ramps. PI. 2, Fig. 6. The ram- 
 part-slopes are planes of$-, passed through the inward lines of 
 the terrepleins. The lines of intersection of the rampart-slopes 
 and plane of site are found in the usual way. 
 
 The ramps Leading from the plane of site to the terreplein 
 Ive an inclination of L-9, and they are 4.30 yards wide 
 Two of them arc placed on the enrtain, one on the flank, and 
 one on the face. 
 
 B98...AxALYsn o* < kwrsTBi « ifom ldovw d bob mi K\< i in n. 
 et, in the plan of his enceinte has adopted dimensions and 
 constructions which give results, for the most part, the same 
 M those of Vanhan and Oormontaingne, making the defei - 
 properties of these different methods about eqaaL Tlie extent 
 of the exterior side, the length of the curtain, the diminished 
 angle, and the dii ned for the flanks, produce a com- 
 
 bination by which an efficient flanking, both as to direction and 
 amount of lire, for the entire scarp, and ■ powerful c 
 upon tie l-way and its glacis in advance of the bastion 
 
 nt. The lines of defence, by this combination, being with- 
 in the effective range of small arms, and the flaaka capabli 
 
 iving a battery superior to the counter-battery that can bis 
 bronght against them from the glacis crest of the oppo 
 end-way. 
 
 •'...The dimensions and form of the profile are those 
 usually adopted for perman< at works, where the embankn* 
 
l^s n..i/.i:t's METHOD. 
 
 arc formed of ordinary earth, and the revetement walls of 
 good masonry. 
 
 They are Mich ae experience baa shown will give durability 
 and stability to the masonry, from the pressure of the embank- 
 ments and tin' ordinary causes of destructibility to which it Is' 
 liable when exposed to the weather; and to the ramparl and 
 parapet the strength to resist the action of the heaviest artil- 
 lery; whilst they offer to the assailed every convenience for 
 their prompt action and the ase of their anus. 
 
 300...The width and Blopes of the ramps are regulated for 
 the passage of artillery. Where the height to be overcome is 
 slight, as that between the terreplein and barbette, the Blope 
 of the ramp may be as great as L-6, ami it> width be 3.30 yards. 
 "Where the height is greater, the declivity of the ramp should 
 be proportionally less steep, ami its width be 4.30 yards at 
 Least. 
 
 301. ..The position of the terreplein with respect to the in- 
 terior crests, is that usually considered necessary t<> give 
 shelter to the troops ami materiel on it. By inclining that of 
 
 the bastion, the materiel and />< rsOflfti 1 on the faces and thinks 
 
 are better covered from the enfilading and ricochet lire than 
 they would Ik- if tin- terreplein was horizontal; as a hall pass- 
 ing Over the salient will reach an inclined terreplein at a point 
 farther fro^i the salient than one which is horizontal. The 
 height, l..~." feet, at which the salient is placed ahove the cur- 
 tain, is as great as can he admitted in a hexagon, the Least 
 polygon to which the tract'- adopted is applicable; because, if 
 placed higher, the plane of the interior crest of the bastion, 
 prolonged hack, would intersect the plane of site in a line 
 Which would fall without the salients of the two adjacent has- 
 tens <.f the polygon, and these bastions would, therefore, not 
 !• the one between them from reverse lire 
 The Blopes, moreover, of the terrepleina keep them in a ser- 
 viceahle Mate, by not allowing the rain-water to collect and 
 
 remain upon them. 
 802...Pabticttlab Conditions ok the Outwoeks. The out- 
 
N0IZ1 l\s M1TFIOD. 109 
 
 works, besides satisfying the general conditions already laid 
 down, are connected with each other by several minor relations 
 of defence and suitableness, growing out of their relative | 
 tions, which give rise to many seemingly arbitrary construc- 
 tions and details for each one. ilie bearing of which cannot be 
 clearly explained until a description of the whole as a system 
 has been gone into. 
 
 303... The scarp walls of outworks, as well as their gor. 
 where they are exposed to, be turned, should not be h\s* than 
 12 feet high, to secure them from a sudden open assault. 
 
 304:. ..Their parapets are of the same form as that of the en- 
 ceinte: and fortlie more important ones, which are much ex- 
 pesed to the artillery of the assailant, of the same dimensions. 
 Jn t' - exposed, the thickness of the parapet may be re- 
 
 duced to L2 feet, or 4 yards. 
 
 ~....T1m terrepleins of the smaller outworks, which are not 
 habitually armed with artillery, should not he less than 8 
 yards; those of the larger should not he less than 1 * > yard-. 
 
 .".oi;...The banquette-treads of outworks, which, like the ca- 
 ponoieres and covered-ways, require a palisading for their 
 greater security from utauU, should be 6 feet wide. 
 
 7...Ti n ati u . PL •:. Figs. 1. -1. The form of the tenaille 
 IS that of CormoiitainirncV front ; the magistral of it> curtain 
 being parallel to that of the curtain of the enceinte, ami the 
 
 the prolongation of the scarp of the 
 tion fao 
 
 -...A ditch of 13 yard- i.- left between the g the 
 
 tenaille and the enceinte curtain, and one of 1 1 yard- between 
 each of its wings and the think.-. Tile magistral of ita curtain 
 is horizontal, and 1 .". feet above the crests of the doable capon- 
 niere. The magistral of each wing is a broken line, the lo 
 point of it being 13 feel above the bottom of the enceinte 
 ditch. 1' and the extremities of i: 
 
 iteriof crest is horizontal throughout, and • I below 
 
 the ftl of tiie enceinte o. The thi< 
 
 parapet, \i feet The w idt h 
 
11" ex's method. 
 
 8.66 yards- The parapet is terminated at the wings by tra- 
 verses LS feet thick, which extend from the interior crest .to 
 the .-carp wall of the wings; the top of each traverse is on the 
 same level as the interior crest The traverses are terminated 
 toward the parapet by planes of l-l. 
 
 809l..To construct the principal lines of the tenaillefrom the 
 preceding data, first draw a line parallel to the enceinte cur- 
 tain, and 18 yards from it. for the gorge of the tenaille curtain ; 
 another line parallel to this, and at s .'i»; yards, is the interior 
 crest, of which the reference is (63.50), as it is 4.60 feel below 
 the enceinte magistral at the cui-tain. 
 
 31<»... A level passage at 31.50 feet below the magistral of 
 the enceinte curtain and at the reference (86.$0), leads from 
 
 the main ditch, between the enceinte and tenaille, under this 
 last work, and through a double caponniere in the main ditch 
 in advance of it. The crests of the caponniere are $ feet 
 abdvethe level of the- passage and at the reference (45.50)) 
 and the magistral of the tenaille curtain 13 feet above these 
 OTCStS, and at the reference (5S.50). The interim- Crest of the 
 tenaille having the reference (63.50), "fs> therefore, ."» feet above 
 its magistral. The horizontal distance, then, between the 
 magistral and interior crest. Art. 05, is 12+3+1.5 = 10.5 ft., 
 6r 6.50 yds.; and as these lines are horizontal, their projec- 
 tions will be parallel and at this distance apart. 
 
 311. ..The interior crest and magistral of the wing will result 
 from the following data: The scarp wall of the wing extends 
 to the to]> of the traverse reference (63.50); its magistral then 
 
 descends from this level in the plane of 1-1, which terminates 
 this traverse, to a level of l;; feet above the bottom of tin- en- 
 ceinte ditch, which; being at this part 8 feet lower than the 
 passage of the double caponniere, and at reference (33.50), 
 
 will give (46.50) tor the reference of the lowest point of the 
 magistral of the wing; the reference of .the point where it joins 
 that of the curtain being, as already determined, (58.50); 
 
 312...Tofind, then, the lowest point of this magistral, draw a 
 line 12 feet, or 4 yard.-, from the extremity of the wing, for the 
 
NOIEET8 .Million. Ill 
 
 exterior line of tlio traverse; parallel t6 tins lino draw another 
 at 17 ft. = 5.<i<; yds., which is the base of the slope of l-l that 
 terminates the traverse, where tins line cuts the line 0/ defence 
 is the required points The horizontal distance between thifi 
 point and the interior crest, calculated in the usual manner, is 
 li'-|-15-r-1.50=2s.:,o k*9.G0 yds. 
 
 318.».Describing, from the point just found, an arc, with a 
 radius 9.50 yards, and from the other extremity of the magis- 
 tral another arc, with a radius 5.50 yards, and drawing a tan- 
 gent to these ares, it will he the inferior erest of the wings. 
 
 314-.. .The gorge line of the wing is not drawn parallel to the 
 interior crest, but determined as follows: From the point, of 
 intersection of the interior crests of the enrtain and Wings, 
 descrihe an are with a radius 8.66 yards; from the point when 
 the enceinte enrtain magistral prolonged cuts the interior crest 
 of the opposite flank, draw a line tangent to this are, which 
 will he the direction of the required line. 
 
 31 5.. .The gorge wall rises to the level of the terreplein. 
 That which terminates the wing is limited by the planes of the 
 parapet, terreplein, and top of the traverse, and is termed a 
 proJUt tr<tll, from the form of its outline. 
 
 mi*!....\n Ai.Y-i- of Oeas THE Tenah.i I . 
 
 The teniiille is taott important as a mask than ns a defensive 
 work. I the postern in the enrtain. and also the ma- 
 
 ny of the flanks and curtain from the enemy's battel 
 which last is ;i!i essential point, if there are interior retrench- 
 ments resting either on the flank- or certain of the enceinte, 
 as it will then he impracticable for an enemy to turn then 
 he cannot make a breach in the enceinte behind the t.naille. 
 . e work it- tire bean upon the ditches and their 
 id it tie. er the retn at of the 
 
 troops from the ether outwork.-. When the ditch. py it 
 
 indispensable part of the front, as t : 
 fori: run he :i--f luhled to 
 
 mameu\ \ when in the ditch* -. 
 
 3 1 7... Yauhau and < we h.i\ 
 
 

 112 Nnl/.ll'- Million. 
 
 the relief of the tenaille as not to mask tin 1 lire of the flunks 
 (»n tlif breach in the bastion. It is on tins principle that 
 Nouret has determined the position of its interior crest, and 
 placed it at 4.50 feel below the magistral of the curtain. 
 
 31 s . ..In regulating its scarp wall, it is supposed that an 
 enemy would attempt an assault from some point in the dead 
 space in front of it ^ and its height is, therefore, arranged so 
 that no pari of it shall be less than L3 feet above any point 
 that the enemy might then- occupy, 
 
 319...The position given to its interior crest still leaves some 
 portion of the masonry behind it exposed; but, were the ex- 
 d {'art battered away, there would be still a formidable 
 height of scarp left to the enceinte, the parapet of which, 
 also, 'would be l>nt slightly diminished in thickness by it. The 
 portion of the enceinte flank exposed, near the shoulder angle, 
 would be very considerable were the exterior slope of the 
 tenaille parapet extended to tin- extremity pf the wing; it is 
 
 to prevent this that a travels is here placed. 
 
 820.. .The tenaille is seldom armed with cannon, although 
 mortars are frequently placed in it; on this account its t>rr<- 
 jiliin is feduced to s . , '>»> yards. 
 
 331.sJSvery part of the ditch between the tenaille and cur- 
 tain should he swept hy the think.-. It is to satisfy this condi- 
 tion that the gorge line of the wing is bq drawn as to be seen 
 hy the piece that flanks the curtain of the enceihteJ 
 
 322.. .The tenaille, although procuring decided advantages to 
 the bastioned form, deprives it of one of its characteristic 
 points — that of flanking every part of the ditch. For, in frond 
 of the tenaille, there is a dead space, where an assailant could 
 
 a-.-eiuhle in Safety to assault it. This defect, however, is of 
 
 trifling magnitude, since, were the tenaille taken, be could not 
 
 e.-tahlish himself in it ; and the width given to the ditch, be- 
 tween it and the enceinte Hank, is such a> to preclude any 
 attempt to e-ealade the enceinte from the top of the tenaille. 
 
 323.. .The terreplein of the tenaille is inclined, for the pur- 
 pose of defiling it from the enemy's establishment on the ter- 
 
NOIZI.I*- M! I IK Hi. 113 
 
 replein of the demilune redoubt. The inclination of the plane 
 of defilement depends on the arrangement of this redoubt. 
 
 824.. .Double Caponwikbe. PI. 3, Figs. 1, 2. The paaaage 
 of the double caponniere is 3.30 yards wide at the bottom, 
 and on the same level as the bottom of the ditch at the middle 
 of the curtain reference (86.50). The interior crests of this 
 work are at 9 feet above the bottom of the passage ; they are 
 horizontal, and their reference | t5.50). In the profile of the 
 caponniere, the base of the interior slope is 0.50 yards; the 
 banquette is 2.0 yards wide ; and the base of the banquette- 
 slope, 3.0 yards; the horizontal distance, then, between the 
 interim- crest and the foot of the banquette-slope is 5.50 yai 
 which, being doubled and added to 3.80 yards, the width of 
 the passage, gives L4.30 yards for the distance between the 
 interior crests, The crests are drawn parallel to the perpen- 
 dicular of the front, and Limited by the curtain of the tenaille 
 on one side and a line drawn parallel to and 3.3<> yards within 
 the exterior side on the other. 
 
 325. ..The embankment of the caponniere is terminated on 
 the exterior by a glads, which is prolonged to the bottom of 
 tin' ditch. This glacis is determined by passing a plane 
 through the interior crest of the capdhniere, and through the 
 shoulder angle of the interior crest of the opposite bastion 
 lowered thn 
 
 .••...']"■■.< caponnien is terminated toward the exterior side 
 by a profile wall along the lift ■. at 8.30 yards within the 
 terio this wall is prolonged from the exterior line of the 
 
 banquette-tread to a point at 2.0 yards beyond the interior 
 
 * this point the direction of th<- wall is changed, 
 that, being prolonged, it may cut the interior oreel of the i n- 
 
 v flank, at a point LO yard- from the should' r The 
 
 remaining part of the embankment on this side is U rmmated 
 in a the plane of which is through the inn 
 
 • of the enceinte curtain, and through a line on the bottom 
 of the main ditrh. at t.O yards within the exterioi 
 plane inl - in a Lineaft, P 2, which 
 
114 1*- Ml THOD. 
 
 is prolonged to it- intersection, &, with a lino. h<\ on tlic first 
 glacis, a1 6.66 yards from the interior crest. A part oftne first 
 glacis ie terminated at this lino, by a plane of l-l : the line of 
 intersection of this plane of l-l with the second glacis, ie pro- 
 longed to intersect ih<' line <•(' the wall directed on the flank, 
 
 which gives the point where this wall terminal 
 
 As the bottom of the enceinte ditch has no! yet been fixed 
 
 throughout, its intersection with the first glacifl still remains to 
 be determined. 
 
 ."! •_'?.... \ \.\ i. v -i- OFTHi Double Caponoteke. The caponmere 
 serves both a^ a commnnication and ;i> a defensive work for the 
 ditch. As the former, the p mould admit of a conve- 
 
 nient circulation, without being too wide, which has determined 
 its width at 3.30 yards. The interior crests should cover the 
 troops within the caponniere from the enemy's establishments 
 on the crest of the bastion covered-way ; a relief of 9 feet lias 
 been found sufficient for this purpose. 
 
 •'!i > S...As a defensive work, it> tire should sweep the ditch. 
 It is for this purpose that its embankments are arranged on the 
 interior as an ordinary parapet ami on the exterior in the form 
 of a glacis. Its banquette-tread is made 2.0 yards wide, as it 
 should be palisaded. 
 
 329. ..In order that the embankment of the eaponnniere may 
 
 not, by its relief, form dead .-paces in the ditch, tin- plane <>t' 
 
 the first glacis is arranged so as to he sWepI by the artillery 
 fire of the opposite flank. The plane of the second glacis and 
 the return wall are so arranged as to he swept by the lire of 
 the Curtain and of a part of the flank. 
 
 The portion of the first glacis, near the extremity, is made 
 
 into ^glacis o&wpe, Leaving a sufficient^ thickness of parapet to 
 
 cover the passage. 
 
 '■VM I. . AI aoisti: w.s oi I >im 1 1 i n i; Scaup AM> CotTNTEBSOAJRP. 
 
 PI. 3, Fig. 3. To construct the magistral of the demilune, two 
 
 points are taken on the exterior side at 103 yards from the per- 
 pendicular; through these points perpendiculars are drawn to 
 the exterior side ; the points where they cut the magistral of 
 
NOIZKlV Mil hod. 115 
 
 the bastioD faces arc joined, and on this line an equilateral 
 triangle is constructed, its sides will give the directions of the 
 magistral of the demilune. The extremity. 1>. of the demilune 
 face, is found by drawing a line at 11 yards without the exte- 
 rior side. 
 
 The counterscarp of the demilune is parallel to the scarp, and 
 at L8 yards. 
 
 331...C<TN U Km AIM" Of THE K\< Tr\TK. PI. 3, Pig. 3. To 
 
 struct the counterscarp of the enceinte, an arc is described 
 
 from the salient of \\\q bastion, with a radius of 26 yards; a 
 perpendicular, ///'.of 6.60 yards, is drawn to the demilune 
 face; if a tangent be now drawn to the are, and a perpendicu- 
 lar be demitted from the point/", on the tangent, their point 
 of intersection./ 1 ', should fall on the line drawn through the 
 extremity of the double caponniere, parallel to the exterior 
 side. The point. y. is found l>y constructing the curve, which 
 i> the locus of the above conditions. The arc, with the tan- 
 gent drawn through/*, is the magistral of the counterscarp. 
 332. ..III. DOUBT "K nil. Pi-.-i xti.uiNo PlAOE OF Ai:M-. PI. 3, 
 
 8. To determine the magistral of the redoubt of thereon." 
 tering place of arms, a line i> drawn through the point, ft, of 
 the demiluni iremity of the curtain, and pro> 
 
 longed beyond the demilune counterscarp. A point. </. i.- next 
 taken on the perpendicular, at 5.0 yards from the demilune 
 salient ; and through this point and a point, <'. assumed on the 
 demiluni counterscarp, an indefinite line is drawn. A Ww- . 
 <1. is next drawn, making an angle of 60" with the line a <\ 
 
 Two lines, '''/'and •''", :uv drawn, the first parallel t<> <• </. 
 
 and 4.30 yards from it : I >nd parallel I 
 
 lg from it. It' the point of into i 
 lines falls on the line drawn through ft, it will he the angular 
 point <•) the redoubt : and the line •' <1\ the magistral <•!' 
 
 If the point ' '. d", ] on the line drawn 
 
 through 1>, then .. I point, <', most be chosen, and the 
 
 sane ii mad-'. The differ 
 
 of a curve, which il I 
 
1 10 NOl/.l.l'- Million. 
 
 conditions; and the intersection of tins curve with the line 
 drawn through 5, will give the required point. Having the 
 face (■'</'. tin- other face is determined as follows: a line is 
 drawn parallel t<» tin- demilune counterscarp, and at 27.0 yards 
 from it ; a point is found on this line, at T.s;; yards from <■' </'; 
 from this point, with a radius of 7.83 yards, an m-c is described^ 
 a tangenl drawn to this arc, from a point on the interior crest 
 of the bastion face, at L3 yards from the pancoupe, is the di- 
 rection of the required lace. </'(/", which is terminated at the 
 bastion counterscarp. 
 
 ::■•::;. ..i'l. 3, Fig. ::. and PI. I, Fig. 1. The ditch of the re- 
 doubt is horizontal; and the reference of its bottom is deter- 
 mined by supposing the plane of the superior slope of the 
 
 bastion face to be prolonged to the enceinte counterscarp, 
 
 finding the reference of the point, d", in this plane, and taking 
 a point 4.50 feet below this; the reference thus found is 
 pT.fiu). The scarp wall of the redoubt is 13 feet high, the 
 reference of its magistral will, therefore, be (70.90). 
 
 334. ..The salient of the interior crest is 5.33 feet above the 
 magistral — its reference is, therefore, (76.23) ; and its projec- 
 tion is evidently the point which we have already determined, 
 at 7. S3 yards from the magistral; The interior crest of the 
 fact-, d' </", has a slope of two feet from the .salient to the ex- 
 tremity of this face, which condition fixes the extreme point of 
 the interior crest at 7.10' yards from the magistral. 
 
 Having the interior crest of one face, that of the other, <t d\ 
 
 is found from the Scale of declivity of the plane of the interior 
 crest. This scale is drawn parallel to the bastion capital, and 
 since we have already found two points of the interior crest, 
 by referring them to this scale we can, as in the case of the 
 bastion, Art. 294, determine any required point of the other 
 face. 
 
 885.. .A small Hank of 6.0 yards is made perpendicular to the 
 line c c", the line of the profile wall of the face, <•' </'. 
 
 336.. .The tenvplein of the redoubt is 8.66 yards wide; its 
 gorge is revetted with a wall 13 feet high. 
 
noizet's METHOD. 1 1 7 
 
 337.. .Analysts of the Redoubt, eto. Having given the 
 construction of the principal linos of the redoubt, we will now 
 give the reasons in snpport of them. 
 
 388... We tir.-t observe that, on account of the ditch between 
 tin- tenaille and the enceinte flank, a breach might be opened 
 in the curtain, by means <>i a battery established on the glacis 
 of the reentering place of arms, if there was no mask between 
 tlic ditch referred to and this glacis. By placing the angle, c, 
 of the redonbt on the line drawn through the extremity of the 
 curtain, and the extremity, 6, of the demilune, it is readilyseen 
 that these two works, bo combined, cover the opening left by 
 the ditch; since it -will he necessary to battle down either the 
 angle </, or the angled, to unmask the curtain. The means 
 here resorted to is of frequent use in fortification ; and the 
 problem may be thus stated: a lint beinggiven, which ispar^ 
 1'inUy covered by an estietiftg mast from foes in << given direc 
 //'<>}>, in mterposi another mate which, combined with tfu first, 
 shall entirely mask tht given line. 
 
 We have thus established that the point. <■', slrall be found 
 on the line drawn through b and the extremity of the enceinte 
 curtain. 
 
 The communication along the gorge of the redoubt to its 
 ditch, is by mean- of stairs placed along the profile wall, <■' <". 
 The width of the stair,- it 2.0 yards. The stairs, like all other 
 communications, to be safe, must be covered from the enemy's 
 lire. The point where the enemy can establish himself, to 
 
 fire mi the -tail'.-, tfl along the CTCSt of the demilune Cover* d- 
 
 way, around the salient place of arm-. It i^ readily seen, 
 from the position of the stairs and the demilune, thai this 
 work will partially cover the stairs; and, therefore, we rdiall 
 only have to Interpose some other mask, combined with it. to 
 attain t: i ;.-k n-.'J ii the point '•, w 
 
 Lj the angle of masonry formed by the counterscarp walli 
 demilune and redoubt; the ditch of the redoubt being 
 
 The position of the point </. through which 
 on the exterior the 
 
118 N.'izi r"> METHOD. 
 
 / 
 
 demilune parapet, that the Use of are drawn through it will 
 paai "Vrr a man's head at the t < • j » of the Btairsi 
 
 839.. .The angle, <\ between the profile wall and face wall, 
 la made 60°, as this is the minimum angle for masonry, to ■- 
 it sufficient strength. The minimum is here taken to bring 
 the face, <•' o?, as far in aa possible, and thereby make the reen- 
 tering as deep as the case will admit of. 
 
 340...The object of the redoubt is to strengthen the covered- 
 way, and iweep with its fire the enemy's establishments on the 
 glacis of the demilune. The principal works on this glacis 
 arc the breach and counter-patteries, which occupy a Bpace of 
 about 17.0 yard.-, estimated from the crest of the glacis j if to 
 
 this we add L0 yards, for the mean width of the co\eivd-way, 
 
 we obtain the distance 27.0 yards, which is the least distance 
 that the salient of the redoubt can be from the counterscarp 
 
 of the demilune, to sweep the entire flank of the batteries. 
 341. ..The direction given to the face, <l' <1'\ is such as to 
 
 allow of its being flanked by the bastion face. The face is 
 thrown out as far toward the salient of the bastion covered- 
 •way as possible, for the purpose of crowding the space along 
 the crest of this covered-way, which the enemy requires for 
 his batteries. 
 
 342. ..The redoubt being directly in front of the bastion face, 
 its relief "should be bo redueed thai the fire of this face may 
 not be too much masked. To effect this, we commence by es- 
 tablishing the bottom of its ditch, so that the point of it 
 nearest the bastion may just be Been by the musketry lire of 
 the face; we then adopt nearly a minimum relief of scarp 
 wall; finally, we arrange the interior crest of one face, so as 
 
 to allow no exterior slope at one extremity, and make the 
 other at the salient 2 feet higher. This slope of - feet and the 
 direction given to the scab' of declivity of the interior crest, 
 determine a plane of defilement for the redoubt, the prolonga- 
 tion of which will pas> at about 3 feet above the salients of 
 
 the two demilunes, which are symmetrically situated with 
 respect to the bastion capital. This is done in accordance with 
 
 
NOIBET's Million. 119 
 
 a principle generally adopted, that when one work is less ad- 
 vanced than another, and commanded by it, ijhe plane of its 
 interior crest prolonged should pass 3 feet above the points 
 which the enemy can occupy on the advanced work — which, 
 from the nature of fche attack, must fall first into his possession — 
 so that he may not have a plunging fire into the retired 
 work, from his establishments, which arc generally about 3 
 feet above the parapet of the work occupied. 
 
 343. ..The small flank of 6.0 yards perpendicular to the pro- 
 file wall, is to obtain a reverse fire on the breach made in the 
 demilune. The gorge of the redoubt is revetted to secure it 
 
 from an assault. 
 
 344.. .Di mii i m Redoubt; PI. 3. Fig. B, and PI. 4, Figs. I. 
 
 2. The salient of the redoubt is 33.0 yards from the magistral 
 of the demilune ; finding a point on the perpendicular, at this 
 distance from the magistral, we obtain the salient. The magis- 
 tral <>f the tace is found by drawing a line from this point to 
 the interior shoulder angle of the bastion. 
 
 .".!.*>... To find the portion of the interior crests of the face, 
 the reference of the magistral must be given, and the scale of 
 declivity of the plane of the interior crest. To determine the 
 first, the salient of the demilune interior crest is placed at 3 
 feet below tbat of the enceinte curtain: this giv for 
 
 the reference of this point The salient of the magistral of 
 
 the redoubt is fixed at B feet below the salient of the demilune, 
 which gives it- reference (70.0). Xhe magistral Blopes from 
 the salient toward the exterior side, and this Blope i> arranged 
 s<> that the point where the magistral cuts the exterior side 
 shall be 5.70 feet, or 1.90 yards lower than the salient; the 
 rence, then, of this point will be (64.80). Having thus 
 point- of thi Tab ita position is fixed. 
 
 846...TV) determim now the interior crest, a paneoupe* of 
 4.:'." yards : - made in the salient of the redoubt, and thi- com- 
 mands the salient of tie' demilune by 1 .6 R et. T 
 then, of the paneoup Prom the pan* to the 
 
 the redoubt, which is on tie 
 
120 Nnl/.l I | MKTHOD. 
 
 of N the interior crest lias a -lope of 1.5 feet, and its scale of de- 
 clivity i> parallel to tin- perpendicular. To find the crest from 
 tin- above 'lata, it may be ebeerved that the problem is similar 
 
 to the one already wived, Art. •_".'!. in the case of the bastion; 
 except here, tin- magistral being an inclined line, the- distance 
 of any one ofita points, to the point on the interior crest, con- 
 tains! in a profile, is not known, sin^e only Ope of the points is 
 n. The following is the method, which applies to all simi- 
 lar eases for doing this: It will he observed that, if the foot of 
 the exterior slope he drawn, it will have the same slope as the 
 magistral. Through the foot of the exterior slope, then, which 
 is known, th* plane of the exterior slope whose inclination is 
 1-1, is passed. If any horizontal line be now drawn in this 
 plane, the horizontal distance, Art. 294, between this line and 
 a known point of the interior crest, contained in a protile, can 
 be readily found. 
 
 To apply this to the ease in point, first drawn the foot of the 
 exterior slope, which is 0.50 yard from the magistral; the re- 
 ference of this line at the salient is (70.0), and at the gorge 
 (G4.30). To obtain the horizontal of the plane of the exterior 
 slope whose reference is (70.0), describe from the point (04.30) 
 an arc, with a radius 5.70 feet, or 1.90 yards; the tangent 
 drawn to this arc from the point (70.0), is the required line. 
 The reference of the pancoupe being (79.50^, its distance from 
 this horizontal line — the thickness ot the parapet being 20.0 
 feet — is 26,1? fret, or S.72 yards; and the reference of the in- 
 terior crest at the gorge being (78.0), its distance from the 
 same line is 8.22 yards; the two points thus found lix the posi- 
 tion of the interior crest of the face. 
 
 347.. .The redoubt is made with flanks, the interior crests of 
 which are parallel to the perpendicular, 22.0 yards in length. 
 To find the flanks, draw a line parallel to the exterior side, and 
 at 22.0 yards; where this cuts the interior crests of the faces 
 will hi' the interior shoulder angles of the redoubt, from whieh 
 the flanks are drawn parallel to the perpendicular. 
 
 
t 
 
 * NOIZEX'S METIImIi. 121 
 
 The magistral of the flank is horizontal, its position is, there- 
 fore, easily found. 
 
 348. ..Joining the point, b. of the demilune, with the extrem- 
 ity of the interior erest of the flank; the direction of the wall 
 which terminates the flank, the ditch of the redouht and the 
 extremity of the demilune is found. 
 
 349. ..The terreplein of the redouht along the face is 8.66 
 yards wide; along the flank the width is 11.0 yards. This 
 terreplein, which is 8 feet below the plane of the interior 
 crest, is called the >'/>/»/', to distinguish it from the remaining 
 interior space, called the lower A rr> j A///, and which is 13 feet 
 below the apper. A portion of the upper terreplein, for a 
 Length of about 14.0 yards from the extremity of the flank, is 
 sustained by a wall of masonry. A portion of the. interior 
 space between the terrepleina of the two flanks, for about 6.0 
 yards from the exterior side, is excavated to the bottom of the 
 ditch. 
 
 350. ..The upper terreplein, along the face, is connected with 
 the lower by a slope of f. Two ramps 3.30 yafdfl wide, with 
 a slope of 1-0, connect the two terrepleins. The details of 
 these constructions are best studied from PI. 4, Fig. 1. The 
 scarp wall of the redoubt is l<i.."><> feet high. 
 
 351... Analysis, in., <>|. the Dimium. Rbdodstt. As the 
 object of the demilune redoubt lias been already explained, 
 the reasons for the constructions employed in determining it> 
 dimensions, etc., only remain to be stated. 
 
 352.. .The redoubt shonld be as advanced as possible, t<> 
 in reverse the lodgments of the enemy on the glacis of the 
 collateral works. To effect this, it> salient is taken ;tt 
 
 yards from the demilune magistral ; this distance is sufficient 
 
 to allow their proper dimension,- to the parts Of the demilune. 
 
 ..The Uic,' of the redoubt is directed on the interior 
 
 shoulder angle of the bsstion, to have its ditch flanked by the 
 
 354.. .In placing the Balient of the magistral at s feet below 
 
 the salient of the demilune, the top of the scarp wail will be 
 16 
 
1 •_'•_' N.H/.Kl B METHOD. * 
 
 nearly on the level with the demilune terreplein. This arrange- 
 nR'iit will force in i enemy, lodged on the demilune terre- 
 plein, either to Lower hie battery, to effect a breach in the re- 
 doubt, or else \<< employ a mine for this purpose; either, ofl 
 which operations will coat him much labor ami Loaa of time* 
 
 355...The LeaM command ha? been given to the redoubt over 
 the demilune, to enable the fire <>i' the redoubt to sweep the 
 demilune terreplein- This command of L.50 feet, with the 
 slope given to the plane of the interior crest, will prevent an 
 enemy from having a plunging lire into the redoubt from his 
 Lodgments in the demilune. 
 
 35G...Thc flanks of the redoubt are principally to procure a 
 reverse lire on the breach in the bastion face; their length es- 
 timated for 8 guns, 
 
 The piece nearest the extremity of one flank should be cov- 
 ered by the extremity of the opposite flank, from the reveres 
 fire which might come through the redoubt from the enemy's 
 lodgment on the bastion covered-way. 
 
 The terreplein of the fiank is made 11.0 yaVls, as it is ha- 
 bitually armed. 
 
 :;.".7...In the outworks, wherever it can conveniently be done, 
 bomb-proof arches should be made, to serve as magazines, 
 shelters, etc. This point has been effected in the redoubt, by 
 the position given to the lower terreplein; by this mean.-, sul- 
 lieient space is gained under the flank for a bomb-proof shelter; 
 The terreplein of the flank is sustained by a wall, which is the 
 interior facing of the shelter. 
 
 :!5S...Tli6 scarp wall of the redoubt might have been re- 
 duced to the minimum dimension of 12 feet. But, on account 
 of its importance, and, also, not to diminish too much the in- 
 terior space, it has been found that the dimensions adopted, 
 
 lt;..")0 feet, best satisfy the requisite conditions. The top of the 
 wall sloj.es toward the gorge, so that at the shoulder angle it 
 may be about 4 feet lower than at the salient; the object of 
 this is, to expose as small a portion of the wall as possible to 
 the eneinv's tire through the demilune cut, which, from its 
 
t 
 Nm/.i t\ Minion. 1_':; 
 
 width, might admit of a breach being made in the redoubt, 
 through it. from flbe enemy's lodgment on the reentering place 
 of arms. It will be seen further on, how the scarp of the re- 
 doubt is covered by the bottom of the cut. 
 
 .'^•...DrMii.rxK „am> us Cut. PI. 3, Fig. 8, and PI. 4, Pig. 
 1. To return now to the demilune, and finish what relates to 
 it and the cut in Its ficfe; % 
 
 86O...T0 construct tin- scarp of the cut, the face, c' d\ of the 
 redoubt of the reentering place of arms, is produced to infer- 
 tile magistral of the demilune; joining this point with the 
 interior shoulder angle of the demilune redoubt, the magistral 
 of the scarp is obtained. 
 
 B61...The exterior width of the cut is found by setting off 
 6.00 yards on the demilune magistral, from the point where it 
 is intersected by the face, <■'<!'. To obtain the interior width, 
 an are. with the radius of L0 yard.-, is described from the ex- 
 terior shoulder angle of the demilune redoubt; a tangent i.- 
 drawn to this are. parallel to the face of the redoubt: this tan- 
 gent gives the direction of a wall which limits the cut on the 
 interior, and also the portion of the demilune, from the cut to 
 the extremity of the face. From the point where the magis* 
 tral of the cut intersects the tangent, set off 11.0 yards, which 
 
 is the width of the cut on the interior. This point joined with 
 the point on the exterior, gives the counterscarp of the cut. 
 
 S68...A parapet BOfeet thick is made behind the scarp of the 
 
 cut. 'I'll.' relief of this parapet IS so determined that, at the 
 
 highest point of the magistral, which is the point on the 
 
 . there shall he no exterior slope : which places the interior 
 
 cr. -t ::.:::: feet above the magistral at this point. The Bcarp 
 
 wall itself, at this point, is 1 •"> let ahove the bottom of the cut 
 on the interior: and the interior line of the bottom i- !■'■ 
 nearly above the bottom of the ditch of the redoubt. 'I 
 conditions ti\ the reference of this point of the magistral at 
 (76.17). The interior crest, which is horizontal, is therefore, 
 at ti ' 
 
 .The bottom of the cut has 1 from 
 
124 trODSBrfl Ml ll!"l>. 
 
 tlic interior to fhe demilune scarp; and the magistral of the 
 cut is parallel to the bottom and at 13 feel above it. This 
 gives the reference of the exterior point of the magistral 
 (71.37): The magistral of the demilune, from this exterior 
 point to the point 5, is heM horizontal and* at the same refer- 
 ence (71.37), 'l'li*' parapet of this portion of the demilune 
 face is Ldfeet thick; its interior crest ie determined by passing 
 a plane through the interior ereet of the parapet behind the 
 cut, ami allowing the prolongation of this plane to pass 8 feel 
 above the demilune salient. The preceding data aiv sufficient 
 to determine the lines in question. 
 
 36 1...A.N \i.y>i- oi i in: Out. The cut isolates the pari of the 
 demilune, near the extremity of the face, from the salient 
 portion ; this part being arranged with a parapet behind the 
 cut, can be defended after the enemy has effected a Lodgment 
 on the demilune salient. The cut thus prevents the enemy 
 from driving the besieged from the redoubt of the reentering 
 place of arms; which he might do, were the whole demilune 
 to fall at once into his possession. 
 
 365. ..The position of the cut is so determined as to allow the 
 face of the demilune redoubt to flank the face, d </'. Widen* 
 ing the cut on the interior facilitates this object. 
 
 By making the interior line of the bottom of the cut 13 feet 
 above the bottom of the ditch, the scarp of the demilune re- 
 doubt is partly covered; and, at the same time, an obstacle is 
 placed in the way of an enemy, who might attempt to carry 
 the work behind the cut by first getting into the cut. 
 
 366. ..It will be seen, in examining the demilune ditch, that 
 the slope, 4.80 feet, given to the bottom of the cut, still leaved 
 a height of 15 to 18 feet between the exterior line and the bot- 
 tom of the demilune ditch, which will secure the cut from an 
 assault on that side. The object of this slope is chiefly so to 
 diminish the height of that part of the demilune scarp, from 
 the cut to the point b, that it may not be exposed to a baft. -ry. 
 which can be placed on the glacis of the reentering place of 
 arms. 
 
NoI/.Kl'.- Ml THUD. 1 •_'."» 
 
 367... As to the interior crest, it is placed as low as possible, 
 and is arranged to cover the interior from the plunging tire of 
 the eneiiiv'w hen established on the demilune salient. 
 
 368...Di:miia'nk. PI. 4, Pig. 2. To return to the demilune, 
 of which only the magistral and the relief of the interior 
 crest at the salient have been determined. 
 
 The magistral at the salient is placed 11.40 feet below the 
 interior crest ; and as the reference of the latter is (T8.0)j the 
 reference of the former will be (66.60). The magistral has ■ 
 slope of 1.50 feet from the Balient to the cut; and the interior 
 ores! is parallel to the magistral ; this condition will determine 
 the interior crest when the salient is known ; and this is ar- 
 ranged so as to have a pancoupe* of 4.80 yards. 
 
 The scarp wall of the demilune is 22.50 feet high. 
 
 869*..The terreplein is 11.0 yards wide. A ramp. 3.30 yards 
 wide, having a slope of 1-6, leads from the ditch of the demi- 
 lune redoubt to the demilune terreplein. The position and 
 arrangement of the ramp are shown in PI. 4, Fig. 2. 
 
 870.. .The terreplein is finished by a slope of earth, instead 
 of being sustained by a wall. This slope is thus arranged : 
 the part terminating the ramp is a plane of 1-1 : the position 
 in the angle is formed by an inclined cylindrical surface, which 
 touches the two interior lines of the terreplein : the width of 
 
 the ditch at the salient of the redoubt, terminated by the 1. .•!-.• 
 
 of the cylinder, is 4.-';^ yards. The remaining portion of the 
 slope is formed of a warped surface, the (dement.- of which 
 are horizontal, connecting the cylinder and the plane of 1-1. 
 Thi.- construction i.- purely arbitrary ; the object being to 
 have the portion of the slope in the salient as gentle a- practi- 
 cable, so that this pint may * i ramp tor infantry. 
 
 -7 1.. .An a i \ -:- "i mi I )i miii m . i k . The principal prop- 
 erties of the demilune were mentioned in describing < !ormon- 
 method; and it was there observed that he improved 
 upon Vauban'a, by augmenting the dim- f 'lie demi- 
 
 lune. Engineers, sine* < ortnontaingne, finding that the d. 
 lunej .-till admitted of being enlarged with . ave 
 
llT, .NMl/l.lV Mi II K.|i. 
 
 accordingly bo determined its dimensions, thai it may be tin-own 
 bo far to the front as will still place the breach, which an en- 
 emy may make in it- face, within the range of the musketry 
 of tin- bastion face. In large fronts, like this nnder considera- 
 tion, the demilune may !>(■ thus made to cover about 80 yards 
 of the bastion faces from the Bhoulder angle, and thuB secure 
 retrenchments resting against this part from being turned by a 
 breach made near the Bhoulder angle. 
 
 872...These considerations limit the salient angle of the demi* 
 lune to 60°, and place the Balient at not more than 210 yards 
 from the bastion face, as this distance will bring the breach at 
 about 180 yards from this face, or within the effective range of 
 musketry. 
 
 373"...The demilune thus arranged places the bastions, In all 
 cases, in strong recnterings; but when the angles of the poly- 
 gon are very obtuse, the faces of the bastions* prolonged, also 
 fall within the salients of the demilQnes, and arc, therefore, 
 not easilv enfiladed. The fire from the demilune Is very effec- 
 tive on the enemy's works along the bastion capitals. Finally, 
 it is a work of which the enemy can only obtain possession 
 after great labor ami loss of time; and when carried, it is with 
 great difficulty that he can render it. tenable, as it is exposed 
 to the fire of the enceinte, within a short range. 
 
 374.. .The demilune, with these advantages, is not without 
 defects. Its faces, from their position, are exposed to an enti- 
 ladingfire; it deprives the curtain of all action on the exte- 
 rior ground ; and it is only when the angles of the bastion arc 
 very open, that the rednterings formed by the demilunes be- 
 come of a formidable character. The glacis 6f the demilune 
 covered-way forms a ridge, which is serviceable to the enemy 
 by masking ''is works on one side of the ridge from the fire of 
 the collateral works on the other. 
 
 Having noticed these general properties of the demilune, 
 the further particular constructions may be examined. 
 
 375...In terminating the lace at 1 1 .< > yard.- from the exterior" 
 side, a passage made along the extremity of this face, and a 
 
not/kt'k METHOD. 127 
 
 face cover for the bastion, of which mention will be made far- 
 ther mi, are allowed for; moreover, the flack of the demilune 
 redoubt, intended to defend the breach in the bastion face by 
 a reverse tire, is unmasked by it. 
 
 •">7<!...The command <>f the curtain over the demilune is re- 
 duced to the minimum ; and to obtain as much interior c|iacc 
 lor the demilune reddidit as practicable, the height of the in- 
 terior crest above the magistral is fixed at 11.4<> fees, the interior 
 space evidently depending on this height. The terreplein is 
 reduced to 11.0 yards, partly for the same reason, and partly 
 to give an enemy great trouble in establishing a battery on it; 
 BSj to do this, he will be obliged to cut away a part of the par* 
 Spot, and will thus expose the rear of the battery to the fire 
 from collateral works. 
 
 .'!77...The terreplein is terminated by a slope of earth, for 
 omy, and. al.-o. because this slope is favorable to offensive 
 
 movements made to drive the enemy from the breach. 
 
 :;7 v ...It is not probable that an enemy would attempt to 
 carry the demilune by escalade ; it i> well, however, to pro- 
 vide against inch an attempt in bo important a work; it is 
 chiefly on this account that the scarp wall is made '-'•_ , .7'<> feet 
 high. This dimension also allows the bottom of the cut to be 
 so placet] that it can be .-wept by the fire of the demilum 
 doubt. 
 
 879..J? \< i -< • 'vi i: m mi Hwijon. PI. 8, Fig. 3, and PL l. 
 Fig. 1. By prolonging the bastion counterscarp to the point 
 /', it serves a- a face-cover to the I icarp, masking it 
 
 frmn the fire of the breach battery erected around the Balient 
 place of arme of the demilune covered-way. The angle,./", of 
 the face-cover is placed on the lame line as the extremity of 
 the doable caponniere, for the purpose of covering the tr» 
 
 ley debouch from the caponniere, from the enemj 
 lishment along the glacii of the bastion cor< red-way. 
 
 ,ht of the wall, at the point f\ ii >" determined as to inter- 
 cept .in appoint ■ the 
 istioa covered-way, and passing at 7 
 
1 38 MOID i\ mi i HOD. 
 
 abovo the bottom of the ditch, at the extremity of the capon- 
 niere. From the point/'', to the gorge of the redoubt of the 
 reentering place of arms, the top of the wall ascends, bo as to 
 cover the ramp Leading from the ditch to the top of the coun- 
 terscarp a( fj ''. and also tlie passage leading from this point to 
 the gorge of the redoubt. 
 
 880... Single Capototcebi \m> Traverse in un Demili 
 hii.ii. Tiiit last passage is also covered from the enemy's 
 
 works on the glacis of the demilune salient place of arms, by 
 
 the crest of a single caponniere, in the ditch of the demilune. 
 He glacis of this work i> determined by passing a plane 
 through the point, (83.40), of the interior crest of the bastion 
 face, found by producing hack the demilune magistral, and 
 through two other points in the demilune ditch : one taken at 
 L3 feel below the ditch of the redoubt of the reentering place 
 
 Of arms; the other, at about L6.60 feet below the cut in the 
 
 demilune. The crest of the caponniere is held in this plane j 
 and in projection, is drawn parallel to the magistral of the face- 
 
 cover, so as to allow space enough between it and the foot of 
 
 the wall, which terminates the demilune face, for a banquette- 
 
 tread of 2 yards, and its slope of l-l ; all of which will require 
 about i.:;m yards. The passage referred to is 4.30 yards wide. 
 
 In order that it shall be covered by the crest of the caponniere. 
 the bottom of it must be at least 8 feel below the crest. 
 
 381. ..The preceding construction subserves two purpoe 
 
 1st, from the position of the glacis it is swept bv the lire of the 
 bastion face ; 30 that the dead space, which was noticed at this 
 
 point of the demilune ditch, in Cormontaingne's method, is 
 here removed ; _d, it coven the troops orossiti'g the demilune 
 ditch from the fire coming from the demilune salient place of 
 arm*. 
 382...As it is important to keep this passage open, even after 
 
 the enemy obtains possession of the demilune, a traverse is 
 placed at the extremity of the capoiiiiieiv, so as to cover the 
 postern which communicates with the tcnvplein of the redoubt 
 of the reentering place of arms. A portion of this traverse has 
 
 
NOlZI/bs Ml I lion. [J9 
 
 to be sustained by a wall, which is so arranged as to afford tlio 
 least possible shelter to an enemy, who. from behind it. might 
 attempt to carry the redoubt by the gorge. 
 
 383.t.The fitoe-eover is terraced, the embankment being 9<66 
 yards thick at top, and sloped inward toward the passage. 
 
 Rbkabk. The details of this part of the construction being 
 rather eomplioated, will be better understood by referring to 
 PI. L, Fig. 1, than by any written explanation. 
 
 8841..A£a.sx in rate Dimium: Rjedoi bt Dttoh. PL 4. Fin. 1. 
 To corer the curtain wall from a fire through the opening be"* 
 twirn the flank and the tenaille, Coming from a battery estab- 
 lished on the demilune terreplein, an embankment is formed in 
 r 1 1 « ■ ditch of the demilune redoubt, tlfee wall, which Bepar 
 this ditch from that of the enceinte, being bttilt high enough 
 to support the embankment. The embankment is sloped on 
 top. and terminates in a point near the demilune cut. being 
 terminated on the side toward the redoubt by :i slope, the toot 
 of which is fc.80 yards from the foot of the redonbt scarp. The 
 
 i< of the embankment i- on the line drawn through the 
 shoulder angle of the redonbt and the angle of the tenaille. 
 
 38. r »...The bottom of the ditch between the embankment and 
 redoubt, is about 12 feet abore that of the enceinte ditch, 
 
 which secures the demilune from being turned through this 
 ditch. 
 
 parating the embankment from the demilune re- 
 doubt, this work b secured from an attempt to carry it from 
 the embankment For the same reason, the gorge wall behind 
 the cut b raised the top .it' the embankment \ 
 
 like fxp rted to in all similar orge 
 
 wall of the redoubUof the reentering place of arms, and the 
 counter-carp of the demilune cut. at shown in the detail.- on 
 PL 4. Fig. 1. 
 
 r...< o\ i km i> u \« ~ PI. 5, Figs. '•-■ The bastioned e 
 
 the interior crest b< ing drawn 
 illel to the connterecarp. 
 
 arms are drs 
 17 
 
13<» Xnl/.l l's Ml IllOIt. 
 
 parallel to the magistral of the redoubt, and -<> yards from it. 
 &89.~The eresl of the demilune covered-way is a broken 
 cremaillere, or crotchet line. The short branches of the ore* 
 maillere are 8.60 yards Long, and are perpendicular to the di- 
 rection of the demilune capital. 
 
 31'< '. -. I i i MASKS' OB mi Ti: LVEBSE8 AMD THE I>1 Ml.i s. The ob- 
 jects of the short branches of the crotchets arc t<> cover the 
 dejUes, or passages, between the ends of the traverses and the 
 cri -t of the covered-way ; and to give a column of fire in the 
 
 direction of the demilune capital. To fulfill this last object, 
 the short branches are provided with a banquette, with a Blope 
 of Only 1-1, to bring the crest of this branch as near as practi- 
 cable to the traverse. A passage of 2.0 yards is left between 
 the foot of the banquette-slope and the wall, which terminates 
 the end of the traverse; the direction of this wall is parallel 
 both to the long and short branches of the crotchets, leaving a 
 passage between it and the long branch. 8.0 yards wide. 
 
 391. ..To find the position of the short branch, the base of 
 the interior slope being 1.5 feet, the bampiette-tread ti feet, 
 the base of the banquet te-slope ',).'>{) feet, and the width of the 
 
 defile 6 feel — IT feet, or 5.86 yards, is the entire distance 
 BOUghf between the crest of the short branch and the wall 
 that terminates the traverse parallel to this branch. 
 
 392. ..The portion ot* the long branch, opposite the traverse, 
 is without a banquette, etc.. for the purpose of leaving the 
 least distance between the crest ot' the crotchet and the tra- 
 verse, so that the defile may be covered in the best manner. 
 To effect this, a vertical wall is placed parallel to the end of 
 the traverse, and at L'.o yards from it, to leave space for the de- 
 file ; this wall sustains the earth, but IS not built up higher 
 than Within t.50 feet of the crest. The. earth of the glacis has 
 the natural slope of 1-1 from the crest to the top of the wall ; 
 the base of this slope, consequently, will be l.. r ><i feet, and a 
 herm of 0.60 feet being left on the top of the wall. These 
 distances, together, give 2.U0 yards for the distance between 
 
NOIZKrV Ml TI!"I>. 131 
 
 the crest of the long branch ami the wall parallel to it, which 
 terminates the traverse. 
 
 393...Ti:\\ i BB81 a OK mi ])i \mi n1 OoVEBB>WAY. There are 
 &>nr traverses on the demilune covered-way; which, to avoid 
 repetitions, will be designated as No. 1, No. 2, No. 3, and No. 
 4 — No. 1 being nearest the reentering place of arm.-. 
 
 :::<l...To construct the crotchets of traverses Nos. 1 and 2, a 
 line, / in, is drawn parallel to, and at 13.0 yards from, the demi- 
 lune counterscarp ; parallel to this line, and at a distance <>f 
 6.60 yards, measured on a perpendicular to the demilune capi- 
 tal, a second line, /'///. is drawn. The salient and Reentering 
 angles of the crotchets, between Nos. 1 and 2, rest- on these 
 two lines. * 
 
 395. ..To construct traverse No. 1, a line, n 7i', is drawn par- 
 allel to /'///', and at 2.66 yards ; from the point of intersection, 
 n, of this line with the cresl of the reentering place of anna, 
 a line, n o, is drawn, so that its intersection, 0, with the demi- 
 lune counterscarp, shall be perpendicular to a line drawn from 
 0, to the point '/, <>n the demilune. The line n o, is the interior 
 cresl of No. 1. The exterior crest, n' o, is parallel to it, and 
 at 6.66 yards, 
 
 ...From the point /''. a> a centre, with a radius of 5y08 
 yards, an arc ia described : a tangent drawn to this arc. pecv 
 pendicular to the demilune capital, gives the short branch of 
 
 the crotchet. 
 
 ;...To construct traverse No. 2: from the extremity of the 
 
 short crotchet, just found, with a radiu.- of 6.60 yard>. an arc 
 
 i:- described ; a tangent, drawn from the point </ t<> this arc, 
 will give, by its intersection, ". with the counterscarp, a point 
 <»f the Interior crest ot No. -; the interior crest indrawn from 
 this point, perpendicular to the tangent. The exterior o 
 Lrawn at t Is from 
 
 -..To obtain the crotchets from any assumed point, 
 of th . with radii of 2.66 and 5.66 yaj 
 
 ribed ; tangents are 'lrawn to the* nun 
 
 the inner extremity of the Bhort branch of No. 1 to the arc of 
 
132 sov/a:i'> mi:iik>i>. 
 
 2.66 yards, the other to the arc of 5.66 yards, and perpendicu- 
 lar to the demilune capital, It these two tangents interoeot 
 on tlt«- Line X ///. then the point nl is one point of the end No. 
 i', and the lii**- /< //' is drawn parallel to the long branch ; it" 
 the t£ do not intersect on /' //<'. then some other point, 
 
 /<'. must be chosen) ami a .similar construction made, until tin- 
 iiitcjxrtidii is found on the line /" ///', which will he the salient 
 angle <>t the crotchets. 
 
 ■■'...'I'., oenstrttct No, 3 and it > orotchets, a point i.- taken 
 on thr .-Imrt branch of (he crotchet last found, at 4.30 yards 
 from i t > salient angle; from this point an arc is described, with 
 a radius of L50 yards; a tangent drawn to this arc from tin; 
 point a, will give the point, ", on the counterscarp, where the 
 interior crest of No. :; is to be drawn, perpendicular t<> tin- tan- 
 gent. The exterior crest of this traverse ia at L '■'>'■'> yards from 
 
 tin- interior crest. 
 
 400...The ahort branches of the cretcheta-of No. 8 and No. 4, 
 have the same direction ai tin- others ; bat they are limited by 
 two lines, one drawn parallel to the counterscarp, and at 1 i.<> 
 yards from it, the other at 6.60 yards from this, measured on a 
 perpendicular to the demilune capital. "These two lines being 
 drawn, the position of the salient and reentering an gleB of the 
 crofchets that rest upon them will be found by a construction, 
 similar to the one just describe^. 
 
 401. ..The reentering angle of the crotchet of No. 2 ia cut oil", 
 1»\ drawing a line through the centre of the arc, and parallel to 
 the tangent drawn to it from a. , 
 
 402.,/To construe! No. 1, commence by finding the foot of 
 its exterior slope. Tins is done by describing an arc from the 
 angular point, <■', of the redoubt df the reentering place of arras, 
 with a radius of 1.30 yards; a tangent drawn to this arc, 
 through the demilune salient, being produced to the covered- 
 
 wav, gives the foot ot' the exterior slope. 'Hie interior crest of 
 
 No. I is parallel to this line; its position is found by allowing 
 
 4.66 feet, or I..V. yards, tor the l>;ise ot the exterior slope, and 
 
 BO fret, or 6.66 yards, for the thickness of parapet Having 
 
btoqdbt's mi nK'ii. L83 
 
 the exterior and interior crests, the point ?i, and the crotchets, 
 a r< • found as in the preceding ess 
 
 K)8...The interior crest of the salient place of arm.- is on the 
 Line, £ r»> produced ; which ie-at L 1.0 yards from the counter- 
 scarp. A pan soupe* of 1.80 yards U made in the salient. 
 
 4('4...Ti; w i i;-i on thi Bastion Co* i m i>-w ay. PL 5, Pig. 
 1. To construct the traverse 1 and its crotchets on thebaatiqn 
 ci,\ iTnl-wav. a line, 1 i\ is drawn at 6.60 yards, parallel bo the 
 crest of the bastion covered-way : the extremity of die trav< 
 
 . i.- drawn parallel to / r, and 2.60 yards from it. From 
 the point /'. <>n the crest of the reentering place of arm.-, the 
 interior crest of the traverse is drawn perpendicular to the baa* 
 ti >n Counterscarp. Tin- exterior crest i* '-'" ltl '■ W ,; - ,;,; yards, 
 from the interior creek 
 
 To find the other branch of the crotchet, n n' is taken, equal 
 to 5.<» yards; a line is drawn throngh r and //, and produced 
 to .v. on the crest of the bastion eovered-<wajy ; an arc, with ■ 
 radius of 2.66 yarda, is now described from /<'. and the tangent, 
 * l, drawn to this arc, is the branch required; 
 
 4<C..( "mm \M- OF mi: ( <>\ iKin-w w a\i> Tn.wi i:h >. PL 5, 
 
 Fig. •_'. To arrange the relief of the covered-way and travel 
 tlie following method is pursued: The salient of the demilune 
 feet lower than the salient of the demi- 
 lune; the reference of this point then ia (tO.60). The interior 
 te of the salient place of arm.- of traverse No. 4. and the 
 long branch between Noe. S and t. are held in the same*pla 
 the icah which ia parallel to the demilune cap* 
 
 ital ; its inclination being determined by placing the extremity 
 the long branch, just referred to. 0.7;, feet lower than the 
 salient of the demilune coven 
 
 i he short branch of the ei - No* 8 1 
 
 • red-waj . 
 the interior crest ol and the long branch, are held in 
 
 the same plane, whoe In ity i- parallel to the demi- 
 
 lune capita . inclination ii such that, 
 
 dated, it will pass 8 
 
134 N.'l/.l l'- Ml -UK il). 
 
 4<>7...The relief of No* - ;ui<l its crotchets ia determined in 
 the BanKB manner a> in the preceding case. The reference el 
 the Bhort branch being fixed a1 (70.S' 
 
 408.. .The Balients of the bastion covered-way, and the re- 
 entering place of arms, eommand the Balient of the demilune 
 covered-way by L.50 feet Their reference, therefore, ie 7 
 
 409. ..Ukmakk.- 09 mi CoVKBED-WAYS AND Ti:.\\i.i;>i>. The 
 
 demilune covered-way is made wider toward the reentering, to 
 cover tlu- traverse defiles with more ease. The width, 11.0 
 yards, of the portion near the salient, makes tlif covered-way 
 bo narrow that, should an enemy liml it necessary to Lower his 
 breach battery into it to effect a practicable breach, he will be 
 obliged to cut away a part of the glacis to obtain sufficient 
 room for his works. 
 
 410...The counterscarp of the redoubt of the reentering 
 place of arms is a slope of earth, so as to make the reentering 
 place of arms more spacious, by joining the ditch of its terre- 
 plein. 
 
 411. ..The interior crests of the reentering place of arms and 
 its two traverses are held in the same plane, whose scale ofde* 
 divitv is parallel to the bastion capital. This plane produced, 
 passes 3 feet above the salients of the two collateral demilunes* 
 from which this place of arms is thus defiled. 
 
 412. ..The crests <»f the bastion covered-way are in the same 
 plane, whose scale of declivity is parallel to the bastion capi- 
 tal. This plane, prolonged, also passes 3 feet above the same 
 points as the last mentioned] and for the same object. 
 
 ll:;. ..The traverses serve as masks to cover the terreplein of 
 
 the COVered-way from ricochet shots; for this purpose, Xos. li 
 
 and .*; may be only 4.33 yards, or l."> feet thick. Hut the other 
 traverses, which close the reentering and salient places of arms, 
 
 being more important, have a thickness of 6.66 yards. As the 
 general height of the traverses is 2.66 yards, it is readily seen 
 that, supposing 1 the extreme limit of ricochet firing to be an 
 angle of 1-10, the traverses should not be more than 2b'. (J yards 
 
 J 
 
NOTZKl's MKIIIol). 185 
 
 apart, in order that a shot striking the crest of one may imbed 
 Itself in that immediately in rear of it. 
 
 414.. .The traverses also servo as a defence : and for this pur- 
 pose arc made like an ordinary parapet. To enable the be- 
 sieged to defend the coverediway, they are palisaded, and 
 barriers arc placed at the defiles. As the means of protracting 
 tin- defence arc only effective when the defiles .-ire perfectly 
 secured from the tire of the enemy, established along the Crest 
 of the salient place of arms, the reason for the particular con* 
 •traction given for each traverse will now be apparent. Hie 
 interior crests of Nos. 1. 9 and 3 are so arranged that they 
 can concentrate their fire on the salient place of arms ; and 
 each traverse i.- so combined with the demilune, as effectually 
 to mask the defile of the one in rear of it. The defile of No. 
 1 is masked by No. -. and a passage of about 2.<» yards at 
 the foot of the h;ui<jiiette-slo]>e < ► t " No. 1 is covered, so that the 
 
 troop.- can pass through this defile in perfect safety. 
 
 41 5. ..The defile No. 2 is less easily covered by No. 3. To 
 effect it. the inner angle ot the crotchets has to be cut off and 
 the banquette-elope suppressed, substituting in its place Btepe; 
 by these means, a passage of l.o yard is •covered, and N". ■'> 
 
 placed not too far from No, -. 
 
 416... As it is hot practicable to cover the defile of No. 8, the 
 
 tion of No. i 18 determined. BO a- to make the salient 
 place of arms a- spacious CM possible. This is done by phi 
 
 4 in a position, to allow its exterior slope to be swept by 
 the fire of the bastion face, penetrating between the salient of 
 the demilune and the angle of the redoubt of the reentering 
 place of arms. 
 
 41 7. ..The defile of the traverse on the bastion covered-way, 
 nt any line of fire penetrating through it 
 Into the reentering place of arm?. 
 
 418.. .The precautions which arc here taken would 1" 
 insufficient, could the enemy, in possession of tin f the 
 
 salient place of arm-. ha\ e a plui red- 
 
 •rmy behind the trav< I- - to prevent tin's that th< 
 
13H Nol/.i •■["- KKTHOD. 
 
 terior crests of the different traverses and their respective 
 crotchets are held in the same plane J which is bo arranged 
 thai the terreplein shall be defiled from the enemy's lodgment 
 
 on the crest of the salient phu f arms. Tin's arrangement 
 
 necessarily places the terreplein between the traverses on dif- 
 ferent level.-; small ramps will, therefore, be necess.arv to ; 
 from one, level t«> the other. They are placed at the defiles. 
 
 41 '.♦. ..The salient ]>laee of arms is inclined for the purpose of 
 partially defiling it from the trench cavalier. 
 
 420.. .Finally, tic traverses are sustained on the Bide of the 
 counterscarp by I profile wall, which is the prolongation of 
 the counterscarp wall; and they are terminated at the other 
 extremity by a wall, so as to make the defile convenient a> a 
 communication. 
 
 421. ..Coi'ntikx u;rs i>i- Tin; Bastion am> Demilcxtb. Hav- 
 ing determined the relief of the covered-way crests, which, it 
 
 may lie observed, is such that, they mask all the masonry Of 
 the scarps, and, at the same time, are BO low that an ciicmy 
 
 cammt. by the ordinary methods in use, obtain a plunging tire 
 
 from them dpOU the terrc|>lcins of the works in their rear, the 
 
 position of the counterscarp carestB can now he fixed. 
 
 I •_'•_'. ..The top of the counterscarp wall should he at least 8' 
 h-ct below the planes of the interior creal of the covered-way, 
 
 and the height of the wall for the body of the place should not 
 exceed 24 feet, and for the demilune it may be reduced to 18 
 
 feet. Tin .-e dimensions will, therefore, be assumed, as the 
 greatest that can he allowed with a proper regard to economy. 
 And a continuous wall of these heights may be regarded a- a 
 
 powerful auxiliary obstacle, in securing the works from all 
 attempts at surprise. 
 
 ■12:;. ..Adopting the limit of 24 feet for the counterscarp of 
 the bastion, it will be seen that the bottom of the ditch at the 
 
 toot of this wall is higher than at the foot of the scarp wall of 
 the bastion face; and, as the bottom of the ditch, at the ex- 
 tremity of the double caponniere, has already been determined, 
 
noizkt's method. 137 
 
 these different levels must be, connected by planes, combined* 
 in the most simple manner, 
 
 •|-_' !...< i M li I - LND BOTTOMS OF THE DrTOHES. PI.-. 4 Mini .'.. 
 
 A dinette, 4.<> yards wide at top, and 3 feet deep, is' made in 
 the main ditch to serve as a drain. A cvJUoert, or small arch 
 of masonry, is made under the double caponniere, connecting 
 the cunette on the opposing .-ides of it. The cunette ifl placed 
 parallel to the bastion face; tin- bottom of the ditch having a 
 slope of 1.50 feci from the foot of the scarp wall to the edge of 
 the cunette, and a slope from the opposite edge up to the foot, 
 of the counterscarp wall. These details will he hest under- 
 stood by referring to I *].->. 4. 5, Figs. 1. The slopes hefre given 
 -erve to keep the bottom of the ditch dry; they a— i-t in ren- 
 dering the breach, made in the bastion face-, rather Btei 
 than if the bottom were horizontal : and, in the passage of the 
 ditch, the enemy's work i- thus more exposed than if the bot- 
 tom were not sloped from the foot of the counterscarp wall to 
 
 the cunette. 
 
 The demilune ditch is arranged upon similar principles. A 
 
 cunette and culvert are placed in it., to convey the rainwater 
 froyi it into the main ditch. 
 
 4_'.V..I'l.\\i - OF THE G The glacis of the covered-way 
 
 may now he considered. < hie principle is chiefly to be attended 
 to in disposing the different planes of the glacis. They should 
 all he swept by the artillery tire of the works immediately in 
 their rear, and by the niu.-k« try lire, at least, of the bastion 
 
 -iL'''>...The glacis of the bastion coverecUway should lie swept, 
 by the artillery of the bastion fa< 
 
 1-7. .The glacie of the re< ntering place of anas should he 
 swept by the tire from it- redoubt. 
 
 4l"v I j the demilune "tier,- more difficulty in its 
 
 arrange ment, owing to the cremaillece form of the interior 
 
 l>e-t method seems the following : plat 
 passed t as to 1 
 
 artiUerj demilun< . 
 
 1- 
 
13S Noi/.i r'a mi thod. 
 
 are connected by another Beries of planes, which are pas 
 through the salient point <»t" cadi crotchet below the plane of 
 musketry fire, of at Least one-half of the bastion tare; and 
 below thai <>f artillery fire, jrf a part of the demilune tare. 
 
 4 :.".'... It will he readily seen, from the nature of this prob- 
 lem, that it admits of many solutions. In selecting amoi 
 them, the following considerations may serve a.- guides. Wlien 
 the planes of the glacis have a very gentle slope, they are bet- 
 ter seen by the works in their rear; but the construction is 
 more expensive, on account of the greater quantity of em- 
 bankment. 
 
 430... When the slope is more steep, the enemy's works on 
 the glacifl are better exposed to the reverse views of the collat- 
 eral works, although not so well seen by those directly in rear 
 of the glacis; but the quantity of embankment is smaller. 
 
 431...0tTLi;rs, ok Soktii: Passages. To communicate from 
 the covered-way with the glacis, an <>utht or 80fii< poesOffi is 
 cut in the least exposed face of the reentering place of arms; 
 and one, also, on the long branch, between the 3d and 4th 
 traverses. They are from 8.30 to 4.0 yards wide. The cut is 
 about 6 feet in depth, the earth being sustained on each side 
 by a protile wall. The bottom of it is a ramp leading from 
 the terrepleiu of the c. Aercd-way to the top of the glacis. A- 
 the outlet is closed by a barrier, it should be arranged at the 
 bottom, to alloW tin- barrier free play in opening ami shutting, 
 
 432...CoMMr.Mi'ATi"\>. There is no part of a fortification 
 where more care and judgment are required than in the dis- 
 positions made to communicate from tin- interior with the out- 
 works. The safety of the besieged essentially depends on a 
 proper disposition of the communications, which should afford 
 vwvy facility for offensive movements, and, at the same time, 
 a Beeute and easy means ot retreat. This subject has been 
 treated with peculiar care by Noi/.et. 
 
 b'l.'b.. Besides the ramps, which have already been explained, 
 DOSteraB and stairs form a part of the system of communica- 
 tion. 
 
 
noizkt's method. 139 
 
 434.. .Posterns, as already lias been stated, arc arched com* 
 mnnicatione of masonry, made under the rampart or terreplein. 
 When these communications are required for the passage of 
 artillery, they Bhould be at least lo feet wide, and 8 feet high 
 under///- crown ot hey of tfu arch. When for infantry, they 
 may be reduced to 1 feet in width, and 6 feet in height, under 
 the key. The arch of the postern is generally a semi-circle, 
 <>r what is called a full centre arcA. i& be bomb-proof , it 
 should be at least 3 feet thick through the masonry of the arch, 
 «ind be covered by at least from 8 to £.60 feet of earth. 
 
 135. ..Stairs are only used in situations where ramps cannot 
 be placed : as for example, to communicate with the interior 
 of works, the gorges of which are revetted. 
 
 Cacti step is generally formed of a single block of stone, 
 which is 2.0 yards long m to* dear\Q.Z0 yard in width, and 
 0.20 yard high. Prom these dimensions of the height, or i 
 and width, or tread, of each step, we obtain the following for- 
 mula for the hase of & flight of steps ', when the height between 
 the two landings is idven, 8-2 // — <». 30 = 1) ase. 
 
 Stairs are not so convenient as ramps J and they are, more- 
 over, liable to be easily put out of order by the effects of shot 
 and shells. 
 
 }.',o...( , .mmi'nk \!io\ OF Tin EnCT in i i" ■ wi 'in THE iMou. — 
 
 The postern of the enceinte lead.- through the middle of the 
 curtain, descending from the plane of sight to the ditch. The 
 inclination of the bottom should never exceed 1-6. The bot- 
 tom should not corns out upon I Level with the bottom of the 
 ditch, l>ut about 6 feet above it — a wooden ramp being need to 
 end from the postern to the bottom of the ditch, 
 
 The width of thifl postern should be 1_ feet, both bn account 
 oft ter circulation through it, and because it may he 
 
 ; as a bomb-proof shelter for the troops on duty. 
 
 I to this postern, both toward the ditch and the 
 
 interior, is by door-ways ; one through the scarp wall, which 
 closes the postern toward the ditch, and one through a 
 tical wall ol ty of the enceinte b 
 
140 noizet's method. 
 
 plein, which closes the month of the postern toward the inte- 
 rior. The earth of the rampart-slope is cut away, to leave the 
 passage t" the postern free. The sides of the cut are sustained 
 by wing walls, which make a small angle with the vertical Wall 
 of the postern mouth. The door-way may be 7.0 feet wide, 
 ami 7.50 feel high. The postern itself being 1" feet under the 
 bey. 
 
 For more security, a partition wall, with a «1 '-way, is some- 
 times made across the postern, about the middle point. The 
 leaves of the folding-doors here have loop-holes to fire upon an 
 enemy, should he, by asurprise, gain possession of the exterior 
 door-way. 
 
 437...Co\|Ml NI.'ATIo.N Willi 1 I! I : Tl N A I I.I.K. A postern, for 
 
 the passage of artillery, is made under the teuaille, and leads 
 to the double caponniere. Two stairs are placed at the gorge 
 of the tenaille, to communicate with its berreplein. 
 
 438...G'MMr.\i< ation with nii: Ti i;i;i i-i.i.in and Diivii Qg 
 
 Tin; Demilune RwJoubt, Two stairs are placed at tlie^orge 
 
 of the demilune redoubt, to communicate with it* terrcplein. 
 A postern for artillery leads from the main ditch to the ditch 
 of the redoubt, under it8 flank, for the communication between 
 the main ditch and the demilune. 
 439...Co.M.Mi mi \ii<>\ 1K0M mi; Enceinte Ditch with nut 
 
 ExTEBIOB. To communicate with the covered-ways, a ramp of 
 earth sustained by walls i> placed along the wall that termi- 
 nates the demilune and its redoubt. This ramp is separated 
 from the extremity of the face-cover by a cut 4.30 yards wide. 
 •1 !<»...( 'ommimca iio.n wnii mi: DEMILUNE Gut. The com- 
 munication with the work behind the demilune cut is by a 
 postern and Stairs for infantry, which lead from a point on the 
 
 ramp just described to the terreplein of the work — passing in 
 
 a winding direction under the tcrreplcin and parapet of the 
 work. 
 
 441...Commi mi ai ions of the Redoubt 01 the Ki:-i mi kim. 
 Place of Asms, etc The passage behind the single capon- 
 niere. in the demilune ditch, has already been described. The 
 
NOIZETS METHOD. 14 I 
 
 passage leads to a postern for artillery, made through the face 
 of the redoubt, to its ditch. From the ditch, a ramp for ar- 
 tillery Ira. Is to the terreplein of the reentering place of arms. 
 At the angle of the redoubt on the demilune ditch, stairs are 
 placed to ascend to its ditch; a ramp for infantry leads from 
 the ditch on this side to the terreplein. 
 
 44l'...To ascend to the terreplein of the redoubt, a small 
 
 bern for infantry is made through the face to the ditch. 
 
 being placed alongside the postern just described ; from this, 
 
 a winding postern and stairs lead to the terreplein of the re- 
 
 doubt. 
 
 Hie foregoing, with what has been said respecting the ca- 
 ponnieresj traverse defiles, etc., completes the description of 
 the communications of the front. This subject may l.e closed 
 with a recapitulation of the principal conditions wlu'ch should 
 regulate every system of communications. 
 
 44.".... Ki m.\i;k> om im. Communications. 1st. Tfn commu- 
 nication* should ?" n their position^ compromise tJu 
 safety ofthi < run ink . 
 
 frequent i i i.-l a l ic< 's ceul d he cited of works which have been 
 surprised by an enemy obtaining possession of the gates. 
 Therefore! too many precautions cannot be taken to secure the 
 principal outlet from the body of the place from similar at- 
 tempt.-. It is on this account that the postern in the body of 
 the place is arranged as has been described, to frustrate any 
 indden attack that might be made upon it. 
 
 i l b..L'd. 77/. communications should admit of a oonv* nu tU 
 
 ibserve this purpose, the dim* •<•.. of the 
 
 posterns, ramps, and other similar works, should be convenient 
 
 for I • which they are app I they should be 
 
 placed in such j directly to the poii 
 
 arrived at In « namii " >rra, dim :ion 
 
 the front, it will be found that th 
 ditions s 
 
 4 15.. .3d. 7 /<< positi 
 
142 noket's method. 
 
 why that when cm enetny gets possession of it. In may ob- 
 tain ik' advantagt by it. 
 
 To be useless to an enemy, the communication, when in his 
 poggi ssion, should nol ofFer a shelter for his works; nor enable 
 liini to carry them on with more ease. Tins end will be ob- 
 tained by placing the communications in a position to be en- 
 filaded by the fire of the works in their rear; and so arranging 
 them as to preserve the counterscarp wall unbroken, by which 
 means any facility for attempts at surprise will be avoided. 
 
 4th. The communications should bt covered from every point 
 when an enemy might establish himself, during th< whole 
 peribd thai they oun h of service to tin besiegers; and they 
 should be swept by th> firs of thi < n<-< info . 
 
 Without these precautions, an enemy might cnt oil' all com- 
 munication from the enceinte with the outworks; and in cases 
 of retreat, the troops could not derive any assistance from the 
 enceinte, if he attempted to press upon them. 
 
 446.. .In covering the communications, existing masses should, 
 when convenient, be used, which form a part of the general 
 arrangement of the works. Examples of this are shown in the 
 manner in which the debouohS from the double caponniere, 
 and also those from the traverse defilesj are covered. In the 
 firsl case, by the angle of the counterscarp wall and the salient 
 of the bastion'; and in the second, by the angle of the profile 
 walls of the traverses and the demilune salient. Sometimes a 
 special mask has to be raised, an example of which is seen in 
 the traverse at the gorge of the red6ubt of the reentering place 
 ofarra8, which covers the door of the postern of the redoubt. 
 
 •1 I7..."'th. The communications should fo so placed as hot to 
 compromise tlu retreat of th troops. 
 
 This is effected by placing the communication in the ree*n- 
 
 terlngS, Which are the most secure points, a> an enemy to 
 
 arrive at them will have to brave a powerful column of flank 
 lire. Barriers, gates, and movable bridges of timber should 
 be placed at Buitable points, to cut off one communication 
 
NOI/.I t's method. 143 
 
 from another; ami thus arrest the progress of a pursuing 
 enemy. 
 
 448...6th. Finally, each work should <« independent qf every 
 cotflmunicatioti, except thi <>n' destined for Us particular use. 
 
 This is ;m important object, as it prevents an enemy, should 
 lie succeed in gaining possession of a communication leading 
 through it. from seizing upon tlie work itself. Examples of 
 this arrangement arc shown in the postern, through the face 
 of the redoubt of the reentering place of arms, which leads i" 
 the exterior, and which is not connected with the small postern 
 destined for the service of the redoubt itself; also, in the 
 postern leading from the main ditch to that of the demilune 
 redoubt, for the service of the demilune. This postern does 
 
 not interfere with the safety of the redoubt. 
 
 -M'.'...r.\ examining the communications of the front, gen- 
 erally, according to these conditions, it will he found that their 
 arrangement i:- a.- judicious a- the nature of the problem 
 seems to admit. 
 
 ■l.'.n... In -,, ,;,,,,; Ri 11:1 n< iimi vis. The front, as it has now 
 been described, appears to be of a character to protract the 
 ■ to the longest duration. When, however, a breach is 
 made in the enceinte, although military usage and a point of 
 honor require of the garrison to sustain, at least, one assault, 
 the consequences of defeat are of too serious a character to ex- 
 • such an effort, unless a place of safety i> provided, into 
 which the garrison may retreat, after defending the breach, 
 and obtain an honorable capitulation. <h\ this account, and 
 to lengthen the defence, interior retrenchments tax made 
 in the bastions. These works may he either of a temporary or 
 permanent character; hut i; led that the 
 
 latter class alone off tele to t : 
 
 former, mor» ! it the bi ould be full, 
 
 that the retrenchment Bhottld be thrown up during 
 an nndertaki lifficulty, both from tl 
 
 the enemy's lire and tie I 
 ordinary dut 
 
1-1:4 NOD5BT8 HBIHOD. 
 
 451. ..Therefore, only the permanent interior retrenchments 
 with a revetted Bcarp and counterscarp will be given : and 
 which may be regarded as an element of a regularly fortified 
 
 front. 
 
 •1 .",_'.. .Xoizet, like Cormontaingne, proposesfour classes of in- 
 terior retrenchments. 1st. Those thai rest against the faces of 
 the bastions. 2d. Those that rest against the flanks. 3d. 
 Those that rest against two adjacent curtains. 4th. Those that 
 comprehend several bastions. 
 
 •!."•:'.. ..Fiust CLA88 RESTING ON Till: FACES. PI. G, Fig8. 1. -, 
 
 and .1. />. Fig. 3. The first class may be either the form of a 
 
 cavalier, shut in by cuts across the bastion faces, or an inverted 
 redan ; or, finally, if the bastion is very open, a small bastion 
 front. Of this class, the cavalier has been generally employed. 
 The cavalier receiving a relief so great as to give it a plunging 
 fire upon the enemy's works on the glacis of the bastidned cov- 
 ered-way ; whilst the interior of the bastion, in advance of the 
 cavalier ditch and of the cuts or ditches across the bastion tcr- 
 replein, between the scarps of the bastion and cavalier, is 
 swept, and the breach that might be made in the bastion 
 salient can be defended from the parapets behind the cuts. 
 These parapets, with the portions of the cavalier faces in ad- 
 vance of them-, forming the interior retrenchment. 
 
 1. vi. ..This class presents the advantages of defending the 
 breach within a short distance, and by enclosing the thinks of 
 tli.' bastion within them, they preserve the thinking arrange- 
 ments of the body of the place until the retrenchment is car- 
 ried. The principal objection to them is that, by a breach 
 made at lite shotllder angle, the enemy can turn them. 
 
 45 5... Second class besting AjGAINST the Planes. PI. 6, Figs. 
 4 and C. The second class may be of an inverted redan, or a 
 small bastion front; or, finally, of a redan resting against the 
 middle of the flanks, its faces having such a direction that its 
 ditch maybe swept by the fire of the flanks of the adjacent 
 
 l>a.-tions. . 
 The last form admits of defending the breach within a short 
 
noi/.kt's METHOD. 145 
 
 distance; it preserves also the flanking arrangements of the 
 enceinte, and can only be turned by a breach made id the cur- 
 tain. To sweep its ditch from the opposite Hank, it will be 
 neog&sary to cut down a pari of the scarp wall of the flank on 
 which the ditch rests^ which will make the height of the wall 
 less than 11.0 yard.-, and somewhat expose the enceinte to 
 escalade. 
 
 1 .■"><!. ..Tmiti> ei.\-- BESTEN& ON 5PW0 aim \< r.\ i ( 'i i;i wins. PI. 
 6, Fig. 4. I>. The third class is usually of the form of a has- 
 tened front ; but as the tire of its-faces would be masked by 
 the curtain of the enceinte, it is generally beet to construct the 
 front simply with a curtain and two flanks. 
 
 Thi.- class being thrown farther from the salient of the bas- 
 tion, does not defend the breach so directly as the two preced- 
 ing; but its position i> stronger, and will force an enemy to 
 employ more means t<- carry it. From its djmensions, it will 
 require more space on the interior, and will he also more ex- 
 pensive than either of the preceding tonus. 
 
 4r»7...Foi inn <i.\— i mi.o-im, >i.vi.i;.\i. Fbohts. The fourth 
 clas-, which is placed in the rear of .-evoral hastions of the en- 
 ceinte, or properly, several fronts, [e a kind of sec. . ml enceinte 
 
 within tiie ftrat. An arrangement of this character would, of 
 course, require a peculiar locality, and would seldom find an 
 application. 
 458... < \ •> •. i .ii i; wiiu Oon i.\ mi Bjjstios F.\< i -. I'l. 6, 
 s. 1, 2. The - work are parallel to those of the 
 
 bastion in which it is placed ; its ditch should be about L8 feet 
 >w the bastion terreplein : it.- scarp wall about l'4 feet high. 
 And it may be I d that ali interior retrenchnu 
 
 to ope - oa obstacle to an enemy, should bav< 
 
 ments of about these dimensii 
 
 '4.'. '.'...The interior crest of I bould be so high that the 
 
 line of fire, from the salient of the cavalier to the salient of the 
 
 bs^tion rn\, red-way, shall pas.- above the bastion salient. I'.v 
 
 the counterscarp ol the cavalier at L4.0 yards from the 
 
 interior crest of the bi allowing L1.0 vard- for the width 
 
 19 
 
146 Noi/.l !*- Mi THOD. 
 
 of tin- ditch, and making the bottom of the ditch 18 feet In-low 
 the bastion terreplein— it will be found that the reference fitf 
 the bottom of the ditch will be (58.50); the scarp wall being 
 et high, the reference of its magistral be (82.50). Now, 
 if the reference of the interior crest be taken at (97.50), or 15 
 feel above the magistral, its projection will be at 33.16 feet, or 
 11.Q6 yard.- from the magistral : and as both the lines arc hor- 
 izontal, parallel to it. Drawing, then, three lines parallel to 
 the bastion interior crest, at the distance above mentioned, the 
 projections of the counterscarp, scarp and interior crest of the 
 cavalier are obtained. The position here given to the interior 
 crest of the face will satisfy the condition first laid down. 
 
 40<>. ..The interior crest of the think Is also horizontal-; its 
 reference, therefore, is ( ( .i7."> ,, i ; the direction of the Hank 14 
 perpendicular to the line of defence of the bastion ; the think, 
 moreover, is not. revetted like the face, but is terminated by 
 prolonging its exterior slope to thenastion terreplein ; the low- 
 est point of the foot of this exterior slope will, therefore, he 
 
 about (T-':. (,i M, the reference of the hastioii terreplein at the ex- 
 tremity of its flank; the least width of the bastion terreplein, 
 between ItB think and that of the cavalier, should be 14.0 yards. 
 If, then, from the interior angle Of the curtain, with a radius of 
 14.0 yards, atn arc be desoribed, and a tangent be drawn to this 
 arc, perpendicular to the line of defence, this tangent may he 
 taken as the horizontal of the exterior slope of the cavalier 
 flank, whose reference is (73.0) ; the interior crest of the flank 
 is drawn parallel to this horizontal, and at 41.10 feet, or L8/f$ 
 vanU from it ; which will be the distance found by calculation, 
 the thickness of the parapet being 20 feet, the superior slope 
 I-*;, and the exterior .-lope 1-1. 
 
 -lol...The lengtb of the flank is found by drawing, through 
 the angle of the curtain, a line parallel to the line of defence ; 
 and where it cut.- the interior crest- of the Hank, will be the 
 extremity of the Hank. • 
 
 1ol'...To terminate the gorge of the cavalier, a plane of 1-1 is # 
 passed through the extreme points of the interior crest of its 
 
noizkt's method. ]47 
 
 flanks. A passage of 4.30 v;inls is left on the bastion tenre- 
 plein/at the gorge of the cavalier, to communicate with it; 
 and also to preserve an uninterrupted communication 1 between 
 
 flic two adjacent curtains. A ramp, 3.30 yards wide, with a 
 slope of 1-6, leads from the gorge of the cavalier to its tcnv- 
 plein. This ramp is generally placed along the capital of the 
 bastion. 
 
 («!3...CrTs t.n the Bastion Fa< k>. PI. 0, FigB. 1. -. To de- 
 termine the cut across the bastion face, a distance of 13.0 yards 
 is set off from the shoulder angle of the bastion, along its inte- 
 rior crest; from this point a line is drawn, making an angle of 
 ]on° with the interior crest ; this line being produced to inter- 
 sect the magistral of the cavalier face, is the interior crest of 
 the parapet behind the cut. The reference of this line where 
 it intersects the magistral is (8*2.50), the reference of the other 
 extremity being (84.0) ; it is held in the same plane with the. 
 portion of the interior crest of the hastion. between the' shoulder 
 angle and the point at 13.fi yards from it; the reference of the 
 shoulder angle remaining as already found; it will he seen 
 that the plane of these two lines produced, passes 3 feet above 
 tlie bastion salient. The thickness of parapet is only \'l feet. 
 
 4&4k..The magistral of the scarp of the cut is horizontal. 
 reference being 70;5O . From the preceding data, its | 
 tion i.s easily determined. A line drawn parallel to the magis- 
 tral, and at 6.60 yard- from it. will he the counterscarp of the 
 cut. The counterscarp wall of the cut i> carried up to the top 
 of the bastion face, and forms a profile wall to sustain the 
 earth. The scarp wall of the cut is of the same height as that 
 
 of the cavalier; the bottom of tin- cut will, therefore, be n 
 speed (52.60), a portion of the ditch of tfrc cavalier face has 
 the same reference: thia portion is found by holding at the 
 . that part of the bottom of the ditch toward the 
 salient which can be swept by the tire of the parapet behind 
 the cut; placing the bottom of the remaining portion toward 
 tin- cut, on the same level as the bottom of the cut, or at the, 
 
1 t8 NOIZET'fl METHOD. 
 
 reference (52.50); the two levels being separated by a vertical 
 
 wall <"> feet high, which retains the earth of the tipper level. 
 465.. .This arrangement of the ditch of the cavalier subject! 
 
 only a part of it to the tire of the parapet behind the cut. By 
 
 placing the door of the postern that leads into the cavalier 
 ditch, at the point where the vertical wall separates the two 
 levels, it will he partially covered from the enemy's lodgment 
 on the bastion terreplein. 
 
 4nV,...The object of the cut is similar to the one in the demi- 
 lune face; it confines the enemy to the salient part of the bas- 
 tion, preventing him from extending his works along the 
 bastion terreplehi, to turn the cavalier by its gorge*; so that to 
 obtain possession of this work, he must make a breach in its 
 face. 
 
 ln'7... There is a dead space in the cavalier ditch throughout 
 the lowet level, which might offer some advantages were. the 
 enemy to attempt to carry the parapet of the cut by escalade. 
 To remedy thi> defect, it has heeii proposed to place a cremated 
 gallery behind the scarp wall of the (ait, to flank the entire 
 ditch. 
 
 468. ..The disposition of tho»cavalier and cuts within the has- 
 tion do not leave sufficient space upon the terreplein of the 
 latter to organize a covered-way. But in the retrenchments of 
 open hastions, resting on the flanks or curtains, to which the 
 form of a tenaille, or a small hastioncd front is given, a cov- 
 ered-way, with a reentering place of arms, closed by traverses, 
 can he organized, which will give considerable additional cori J 
 lideiice and security in the defence of the broach in the bastion 
 with the bayonet— as this covered-way will cover the retreat 
 of the troops, guaruing the breach, into the ditch of the en- 
 ceinte—whereas, when the counterscarp is not secured in this 
 
 way, the retreating body run the risk either" of being cut off or 
 
 of having the enemy follow so closely on their heels as to force 
 
 their way into the retrenchment, and deprive the defence of 
 .this last resort for making favorable terms of surrender. » 
 469. ..The organization of these covered-ways presents no 
 
; 
 
 CHA88ELOUP 8 METHOD. 14-9 
 
 peculiarity. They should, as far as practicabley'be defiled from 
 the besieger's lodgments with the bastion assailed. 
 
 CHASSELOUFS METHOD. 
 
 +7<)...Ohasse1onp was one of the most distinguished engineers 
 under Napoleon, aTid had the principal charge of the fortifica- 
 tions constructed by tHe French in the north of Italy, whilst it 
 was i pari of the French empire. His views are to be gath- 
 ered chiefly from some short memoirs published without his 
 name, in which are to he found many of the Leading ideas of 
 pal later engineers of the French school, and what is now 
 termed the German school. 
 
 4?l...Chasse)oap adheres to the bastioned system as the 
 basis of his enceinte, in which, however, he proposes the fol- 
 lowing modifications of the combinations usually admitted by 
 his predecessors, viz: 1st, in giving a greater Length to the ex- 
 terior side, which he p/oposes to vary, if necessary, bet* 
 440 and 660 yards; 2d, in so arranging the plau of his en- 
 ceinte that the portion of the bastion faces toward the salients 
 shall be covered by the demilunes from enfilading views: 3d, 
 in throwing hack the parapets of cerURn portions of his front, 
 which are exposed to be breached, so far to the rear that when 
 the scarp wall is battered down the breacfl will still be cl 
 by the parapet : 4th, in arranging the tenaille wit) sted 
 
 flanks solely for ditch defencej which ! by a n 
 
 from the counter-batteries at the salient of the bastioned • 
 ered-way; whilst by openings pierced in the mask, the lii 
 the think- can be din ctcd on the point to be attained • 5th, in 
 placing in the main ditch a caseraated caponniers t.» obta 
 
150 : "i r"- mi ["HOD. 
 
 iwi'M' fire on the breaches in the bastion faces; 6th, in isolat- 
 ing the main ditch from the ditches of the outsorts, covering 
 it and the caponniere by a covered-way, organized with case- 
 mated traverses and redoubts for defence; Tth, in detaching 
 the demilune from the enceinte, throwing it bo far forward as 
 to cover the bastion faces from enfilade, and in placing in tlio 
 demilune a casemated redoubl to procure reverse views on the 
 approaches on* the bastion salient.-; 8th, in organizing the 
 demilune covered-way in the same manner as that of the en- 
 ceinte; 9tb» in i placing within his bastions strong interior re- 
 trenchments, with casemated skelters for the artillery in 
 reserve, and defensive casemated quarters for the garrison* 
 
 47l\ Plan. The exterior side, PL IT, X Y, is taken at 580 
 metres I French); the perpendicular, Z U, is $ of X V; a por- 
 tion of each face. A'///. Ym\ equal to 60m., lies on X )': from 
 in and //// lines of defence are drawn through U, on which the 
 interior portions of the faces, each 1 ( W > in. , are set otf; the 
 flanks are drawn perpendicular to the lines of defence, and are 
 about 48 in. 
 
 -173. ..The tenaillc is separated from the curtain by a ditch 
 of 1" in., and from the thinks by ditches of L5m. The rear 
 portion <•. Figs. 1, % of the flank, is casemated tor three guns, 
 each casemate being open to the rear; an open court. <. of' a 
 rectangular shape, is left opposite the # casemates, in front of 
 which is the mask, </, pierced with arched openings, through 
 which the shot from the casemated guns are directed. The 
 gorge of the tenaillc has a counterscarp gallery. 
 
 474. ..The salient, #, of the capoiinic»e in the main ditch is 
 
 at 55 m. from Z, on the exterior side ; its faces, .v. /•'. are 65 m., 
 
 and directed on points Q i (/, at 5(1 m. from tin- bastion shoul- 
 der angles ; the flanks are parallel to the perpendicular of the 
 front, and 60w. The parapets of this caponniere are thrown 
 hack from the scarp wall to increase the difficulty of the breach J 
 the parapets of the faces being higher than those of the thinks, 
 to cover them from enfilade \iews. The masonry of the thinks 
 of this work is covered by a glacis y zf, which is revetted, 
 
 
CHASSELOtrr'a method, 151 
 
 leaving ditches of 5 m. between it atfd the scar]) and counter- 
 scarp of the enceinte, and of 10 in. between it and the 0&pon> 
 nieiv flank.-. 
 
 47-b..The counterscarp 6f the main ditch is 20m. wide at 
 the salients, ami directed on the flanks of the capouniere at 
 points 5 in. from the shoulder angles. The ditch qf the capon* 
 nieiv at the faces is Id m. wide. 
 
 47n\..The covered-way lias a reentering place <>f arms at the 
 reentering between the counterscarps of the enceinte and ca- 
 ponniere feces, which extends to within 50m. of the front S\ 
 A salient place of arms, of a polygonal form, like that of the 
 demilune cvend-way. hut not represented on Fig. 1, is ar- 
 ranged in front ot each ha-tioned salient. Each of these 
 places of arms, Figi 4, is odcupied with a polygonal easemated 
 redoubt. Tin 1 branches <»f tin 1 covered-way. between the 
 places of arms, are broken into a ere maillere line, the longer 
 branches of which, prolonged, fall within the bastion salients. 
 Tra\ mated fiif reverse fires or of the ordinary 
 
 traction, are place/1 in the enlarged portions of the cov- 
 ered-way formed by the Ion-- and short branches of the ere- 
 maillere. The directions of the crests of the covered-way, and 
 their lengths, are given by the dimensions on the plan. 
 
 •177. ..Tiie salient, J\ ot' the demilune, is at 17<un. from the: 
 
 point 8', on the ca]>oiini7re countei>ear|> ; its faces are direct. d 
 
 on points j?//, at LOO a. from the bastion shoulder angles. A 
 cut of .'.in. is made in each face of this work at 7<Un. from 
 the salient. The faces are prolonged 60 m. beyond the cut, 
 and are terminated l.v arcs described from the shoulder ai i 
 the demilune redoubt and lines drawn from these centr 
 points on tin- bastion capitals, at 40 tn. in advance of the salient 
 place of arms. Within the salient of the demilune a cure 1 
 traverse is arranged, with conntersloping emh for how*- 
 
 it/er firing along the capitals, in rear of which 18 a small . 
 d redoubt, /.'. Tin- demilune ditch is iOttl. v, 
 
 478. ..The ditches of the demilune redoubt, I s m. 
 
 wid. >f this work are '-V1 in.: its flank-. '_'" m. 
 
1 •"'•_' < ii \ — n."i p'fl mii mmi>. 
 
 flank.-. Fig. .".. are casentated for - guns. The gorge of the re- 
 doubt is a .- m t ; 1 1 1 bastioned front. The faces and flanks have aa 
 .open defence covered by a parap< t. 
 
 47 , .'...Thc demilune covered-way is organised Like that of the 
 
 inte, with casemated redoubts, A', />''. in the salient and 
 
 reentering places of anus. Between these' redoubts are two 
 
 traverses, « A, <t /// the latter cover* the masonry of the re* 
 
 doubt, J', and doses the reentering places of arms. 
 
 480.. .The glacis of the enceinte slopes off toward the gorga 
 of the demilune and its redoubt, So thai all the rear of these 
 wbrks is exposed t<» the face of the enceinte. 
 
 481... Besides the ordinary open communications, Chas 
 roup's front is organised with a »erj extrusive combination <>f 
 posterns and galleries for scarp and counterscarp defences and 
 mines, both for the Bervice of the defences of the enceinte and 
 of the outworks. 
 
 £68...The principal features of Ghasseloup's combination^ 
 consist in liis mode of olosfng the opening for breaching the 
 
 bastion faces, as scciitin X'anhan's fronts,, through the demilune 
 
 ditches, by throwing forward the demilune as a detached 
 work : in his organisation of his covered-ways with casemated 
 redoubts, and oi his demilune re'donbt with casemated flanks 
 having reverse views on the bastion glacis; It has been ob- 
 jected to the position he gives the demilune that both this 
 Work and its covered-way are exposed to be carried 1>\ an 
 open assault at the gor^e, in which case its redoubt would 
 readily fall, and the advantages proposed be lost; also, that 
 the casemated redoubts in the eoveredrways will be so 
 damaged by the ricochel fire of the enfilading batteries as to 
 be useless when the covered-way is attacked. 
 
HAXOV METHOD. 153 
 
 HAXO'S METHOD. 
 
 483.. .General ETaxo holds the first rank among the more r& 
 cent engineers of the French b61ioo1. Having served under 
 Chasseloup in tlie construction of the fortifications of Northern 
 Italy, he' subsequently acquired a distinguished reputation by 
 hie services in the Peninsular war, whore he was engaged in 
 seven] of the remarkable sieges of that epoch, and he finally 
 became President of the Board of Engineers, and in that capa- 
 city directed several of the most important fortifications of 
 I <latc in •France. 
 Nothing of General Haxo's views on the subject of fortifica- 
 tion came before the public during his life. The front which 
 ■•companies this description he had engraved.) &nd copies of 
 it distributed among the officers of his corps, but under an in- 
 junction of Becrecy. 
 
 •im...TYan. Tire sxt e ri o r>Bide, 1h of the enceinte, "PI. 18, 
 
 '.:.l v yard-: the lines of defence, C //. D 6?, arc directed 
 
 On the point />'. at 18.T2 yards from (". or one-ninth of the 
 
 i the fa< ' E and /> F\ are 7l.-"._! yard-: tin 
 
 flanks I: < > . /- If. are perpendicular to the lines of defence. 
 
 |$5...The tenaille consists of a em-tain and flans 
 revetted only on the exterior of the two flanks; it is separated 
 from the curtain <>f th<> enceinte by a ditch 18.11 yards wide, 
 and fn»m the flanks by one of 6.6U yard.-: the Hank- of the 
 tenaille are abonl 8 feet higher than its curtain, and an ar- 
 .-■•d for three guns. The lout of the exterior the 
 
 tenaille em: sch side the 
 
 h ;it wall Of the Hank 0< 
 nn rices. 
 20 
 
154 HAXo'e METHOD. 
 
 486..,Gounterguards are placed in front of the bastions; the 
 (fitches between them and the bastions Ik-mi-: 1»>.;'.0 yards wide 
 at the salient, and their counterscarps being directed on a point 
 J >" . 38.25 yards from ( " ; the salients of the countergaarda are 
 on the line -I B, parallel to C IK and {!» yards from it: the 
 faces A A". 5 .'/. are 138.81 yards, and parallel to the coun- 
 terscarps directed on />", which form the gorge walls of the 
 connterguards ; the flanks A*/.. .'/ .V. an- perpendicular to 
 the exterior side, and are terminated on a line parallel to it 
 through the shoulder angles of the bastjon& 
 
 l v 7...An elbow cut, 5.46 yards wide, is made across the 
 counterguaxds at 84.16 yards from the salient ; the portion of 
 the counterguard behind the cut is arranged for cannon. The 
 ditches of the connterguards are 21.86 yards wide at the aa* 
 lients; the counterscarps are directed upon a point, 0'\ at 
 ISM yards from C". 
 
 &88~.A casemated eaponniere is placed in advance of the 
 connterguards, the middle of its gorge being on the line, A B, 
 joining the salients of the counterguatds, and its salient, P, at 
 t03.83 yards from O / Its feces, /', JJ\ are 29.51 yards !• »ntr, 
 and directed on points at 5. 16 yards from the shoulder angles, 
 A'..)/, of the connterguards; its flanks, TJ\ V, are 36.07 yards 
 long, and perpendicular to the exterior side. 
 
 489..iTo construct the demilune, points .)/", .)/'" are taken on 
 tin- bastion faces at 13.58 yards from the Bhouider angle, and 
 on the line joining them an equilateral triangle is formed, the 
 vertex of which, .//, is the salient of the demilune, and the two 
 sides' the directions of the faces, // - s ', // 7\ which are Id 
 
 yards long. An elbow cut, 5.46 yards wide, is made on eaob 
 face at l'Gd.8 yards from the salient 7/, and separates the por> 
 
 tion -/ from the salient. 
 
 Intl.. .The salient, Q, of the demilune redoubt is 55 yards from 
 the salieat, J\ of the eaponniere; its faces, Q, U, are parallel 
 to those of the demilune, and 65.58 yards long. The iianks, 
 U V, X J", are parallel to the capital, and terminated on 
 lines, x x', drawn from ,t- on the counterscarp of the redoubt to 
 
HAX0 8 METHOD. 1 *'."> 
 
 %' on the line A /?, tit 6.56 yards from tlic flanks of the capon* 
 mere. 
 
 l'.»l...Tlie counterscarps of the counterguards, from the points 
 »". <"', on the prolonged faces of the demilune, arc directed on 
 points <m the flanks of the caponlriere, at L0.93 yards fffem 
 their extremities, to points /', al 13.11 yards from these flanks; 
 and from f they are broken parallel to the flanks, and con- 
 tinned to g on the line x ri. 
 
 492...A casemated redoubt is placed lb each reentering place 
 of arms; its face, b <\ is directed on a point, /. at 36.07 yards 
 from «", and is 39.35 yards lone;: the other face, h £, is perpen- 
 
 dicular to b c, and 21.66 yards loner. 
 
 493.. .A casemated redoabt is also placed in the salient place 
 of arms of the demilune eovered-way. Tlie covered-way and 
 thetreentering places of arms are arranged in the usual manner 
 for sorties, and with trav. i 
 
 ■41*1. ..Interior retrenchments are arranged in the bastions. 
 Tn the one on the right, the parapet of the flank is broken to 
 increase the amount of flank tire. In the one on the left, a 
 high cavalier is placed, having one tier of Casemated tire, with 
 earthen embrasures flke those already described, and which. 
 
 from their having* been introduced by Ha\o. are known as the 
 
 Elaxo casemate, with an upper tier of uncovered fire. 
 
 The ditcher- of thi Dohments are swept t'rom the oppO- 
 
 ■.'... .1 1 ;i\< > cas< mat - are placed in the salients of the eottnv 
 terguards and the salient of the demilune. 
 
 1'.H;...'l'he portions of the curtain parapet of tl nceinte, 
 
 near the curtain j ire retired to give a more effective dl- 
 
 tion to the guns on these portions, and t.. lengthen the par- 
 
 the flanl 
 407... The oommunicatiou from | ate to the main ditch 
 
 is by s postern under the curtain. The communications with 
 the count rguardi and other outworks are through the ditch. 
 between the flanks of tb< 
 inunlcatiou in trout of th< fa tiaille hem- by the i 
 
156 IIAXo's MITIIOD. 
 
 I, I of the glacis in front of it, and by the traverse B, and that 
 across the main ditch to the main caponniere by the double 
 caponniere A'. 
 
 498. ..The ramps, stairs and other passages leading to the 
 tenrepleins of the different works are indicated Oil the plan, 
 and are so placed as to satisfy the conditions laid down for 
 these important elements of a front. 
 
 499. ..The plane of comparison to which the plan is referred 
 is taken at 60 feet below the plane of site. The relative com* 
 mand and the relief of the enceinte and other component parts 
 are thus easily deduced ; and it will be seen that every ad- 
 vanced part is well swept by the fire of the more retired parts. 
 
 500. ..From an examination of the plan, it will be further 
 apparent that, by the position and length given to the faces and 
 flanks of the bastions, the former arc less exposed to eniila4ing 
 views, and the lire of the latter is considerably increased, as 
 compared with Cormontaingne's method and the subsequent 
 modifications of it ; this increase in the number of guns that 
 may be brought to bear on the positions of the besieger is far- 
 ther increased by the flanks of the tenaille, those of the coun- 
 terguards, and the flanks of the cavalier? 
 
 501. ..The counterguards, with the tenaille, mask completely 
 the scarp of the enceinte from any position that the besieger's 
 batteries can occupy beyond the main ditch. All the out- 
 works exterior to the counterguards are well swept and flanked 
 by the lire of the latter. 
 
 502. ..The batteries of the flanks of the casemated caponniere 
 sweep effectively every point in advance of them, and see in 
 reverse the breaches that can be made in the counterguards. 
 The scarp of this work, as well as that of the counterguards, is 
 masked by the plan and relief given to the counterscarp of the 
 main ditch and the covering masses of earth behind it, from 
 the besieger's batteries on the crests of the bastion and demi- 
 lune salient places of arms. 
 
 503. ..The demilune, from its salient position, has strong re- 
 verse views, upon the glacis in advance of the salients of the 
 
CHOUMARA S METHOD. 157 
 
 enceinte, from the casematcd battery in its salient ; whilst the 
 mass of this battery serves as a traverse to cover the portions 
 of the faces in rear of it from enfilading fire. The demilune 
 redoubt serves the usual purpose of this work; its flank is 
 casematcd. « 
 
 604... Although not clearly indicated on the plan, the para- 
 pets of those portions oY the works exposed to be breached are 
 thrown back from the scarp wall, and a chemin de ronde is 
 firmed at the foot of the parapet. By this disposition, a 
 breach, when made, will be more difficult of assault; the re- 
 tired position of the parapet will be less exposed to ricochet 
 fire, and the ch< miit cU ronde will afford both greater security 
 from surprise and a good position for sharp-shooters against the 
 trenches. 
 
 505. ..It is estimated that, by allowing the usual progress of 
 the besieger's approaches, Haxo's front will recpiire about 50 
 days for its reduction. The besiegers, besides the ordinary 
 trenches, batteries and descents, will have to resort to at least 
 five epochs of breaching batteries: lit, for opening the demi- 
 lune and the redoubt of the salient place of arms ; 2d, against 
 the demilune redoubt, the portion of the demilune in rear of 
 the cut, and the redoubt of the reentering place of arms ; 3d, 
 against the counterguards and the casematcd caponnicre ; 4th, 
 against the bastion faces ; and, 5th, against the interior re- 
 trenchments. 
 
 CHOl'MARA'S METHOD. 
 
 50f>...Choumara.a French officer of engineers, of distinguished 
 abilities, is the author of several remarkable memoir* on the 
 
158 CIlnlM \K \"> MIT!Io]>. 
 
 defects of tlio bastioned system, and tlie moans by which they 
 may be removed, and verygceal additional strength lie thereby 
 given to the defences. IIi> propositions for this purposo 
 
 may lie briefly stated as follows : 
 
 507.. .1st. That part of iB permanent work which can un- 
 dergp no modification during the progress of a siege is the 
 masonry, and it may, therefore, be regarded as the really per- 
 manent feature; all the parts of earth, as the parapets, etc., 
 being snsceptible of snob modifications as circumstances may 
 demand. 
 
 This Choumara terms the independence of the parapets as 
 respects the scarps. This latter, upon which the security of 
 the work against an open assault or a surprise depends, must 
 necessarily receive a direction, such that it can be swept by 
 the flanking arrangements, a necessity that does not exist for 
 the parapets, which may receive any direction compatible with 
 the interior space. 
 
 The parapets may, therefore, be thrown back from the 
 salients, as in the bastion, PI. 19, Fig. 1, and receive a cur- 
 vilinear form to throw a greater volume of fire in the direction 
 of the capital ; or they can be retired from the faces, as in the 
 bastion, Fig. A, for the purpose of giving them such direc- 
 tions that their prolongations shall cut the adjacent demilunes, 
 and thus be masked from enfilading views; or they may be 
 prolonged so as to afford a greater column of flank fire, as in 
 the flanks 7, Fig. 1 ; or they may be broken into any direc- 
 tion for the same purpose, or to give a more effective direction 
 to their tire; or, finally, they may be thrown back from the 
 scarp walls instead of resting immediately upon them, and 
 thus render a breach less practicable, since the wh.ole, or a 
 portion of the parapet, will still retain its place after the 
 breach has been made in the scarp — depending on the dis- 
 tance at which the parapet has been moved back. In all of 
 these cases of the application of the independence of the para- 
 llels, Choumara proposes to convert the space left between the 
 foot of the parapet and the scarp wall into a chemin de ronde, 
 
choumaea's Mi/iiKin. 159 
 
 or corridor, which is covered in front by a slight parapet, and 
 from enfilading fire, by a bonnet of suitable height at the 
 salients, as in Figs. 1, A, B, etc. This corridor is occupied by 
 sharp-shooters, to annoy the besieger's trenches. Further- 
 more, Choumara regards the corridor as an additional security 
 against surprise and escalade. 
 
 508. ..2d. Choumara proposes to place high traverses in the 
 bastion salients, to cover the faces from enfilade, and the 
 flanks from reverse views; and similar traverses at the 
 shoulder angles, with the same object. These he also pro- 
 poses to casemate, or else construct with blindages for artillery 
 to obtain a lire in the directions of the capitals, and reverse 
 views on the demilune glacis and the breach in the bastion 
 face. As these traverses, from their height, might give the 
 besiegers in possession of them a plunging fire on the bastion 
 retrenchments, Choumara proposes so to arrange them that 
 they can be readily destroyed at any moment by mines, or, if 
 of timber, be burned. 
 
 509.. .3d. To mask the masonry of the enceinte and demi- 
 lune from breaching batteries, erected in their usual positions 
 along the crests of the glacis, Choumara proposes to form what 
 he terms an interior glacis, or covering mass of tarth, in the 
 ditches, the crests of which shall mask the masonry of the 
 scarps from the positions in question.; and the upper surface of 
 which, forming a glacis, shall be swept by the fire of the works 
 in its rear. In this manner, Choumara proposes to force the 
 b< siegers to the difficult operation of making lodgments in this 
 sis, to obtain suitable positions for their breaching batteries. 
 
 .Mo... }th. Choumara proposes, by a judicious selection of 
 positions for some of the outworks, to occupy those positions 
 on the exterior whidi are most favorable to the sharp-shooters 
 of the besiegers, and thus cripple this important arm of the 
 attack. 
 
 511.. .6th. By giving gi tent to the exterior side, and 
 
 a more retired position to the curtain, which is also to be mads 
 as short as possible,! houmara proposes to obtain bastioi 
 
L60 CHOUMARA S METHOD. 
 
 ample size, not only, to admit of the modifications he proposes 
 for the parapets, traverses and ckemwts de ronde, but for strong 
 interior retrenchments, so organized with bomb-proof ■shelters, 
 ami arranged defensively toward the interior, that each bas- 
 tion will admit of a defence to the rear at its gorge, after the 
 besiegers may have effected a breach at other points, and 
 penetrated within the enceinte. 
 
 512. ..Plan. In adapting these propositions to a bastioned 
 front, Choumara proposes, in order to obtain the requisite room 
 in the interior of the bastions and a large increase of flank fire, 
 to take the exterior side from 400 to 600 metres, French. In 
 the front, Fig. 1, PI. 19, for example, the exterior side is 440 
 metres ; the lines of defence are drawu through a point on the 
 perpendicular of the front at 74 m., or 1-6 of 440 in. within 
 the exterior side ; the faces are 150 m., and the flanks, drawn 
 perpendicular to the lines of defence, are 85 m. — a length 
 which prolongs them 35 m. within their intersections with the 
 lines of defence. By this construction, the curtain, which will 
 be 115 m. long, will be well swept, and the gun at the curtain 
 angle can be brought to bear on the one of the besieger's coun- 
 'ter-battery against the flanks which are furthest out, thus giv- 
 ing a very great preponderance in fire to the flank over the 
 counter-battery. 
 
 513.. .The deep reentering thus formed between the flanks 
 and curtains, gives ample room for a tenaille with flanks for 
 four guns ; these guns are covered in flank by a traverse. The 
 tenaille is not revetted in front of its curtain and flanks, or at 
 its gorge. Tt masks sufficiently the scarp of the flanks and 
 curtain of the enceinte, to prevent any danger to the latter 
 from the destruction of the portion of the scarp wall tnat can 
 be seen over the tenaille. 
 
 514.. .The salient of the demilune is the vertex of an equi- 
 lateral triangle, the base of which is drawn between two points 
 on the bastion, faces, at 18 m. from the shoulder' angles. The 
 faces of the demilune, D, are 144 metres, and revetted. The 
 parapet of the demilune is thrown back from the revetement, 
 
choumaka's method. 161 
 
 leaving a corridor covered by a parapet at tlie foot of its ex- 
 terior slope. The parapet is broken near the gorge, so as to 
 give two short flanks of 13 m. perpendicular to the exterior 
 side. The salient is occupied by a easeniated traverse with 
 flanks for three guns. This traverse masks the interior of the 
 demilune and the Corridor from enfilading views. A disposi- 
 tion is shown for cuts across the demilune faees, the parapets 
 of which are to he thrown up after the siege commences. The 
 demilune ditch is IT m. wide. The portion of this ditch 
 toward the gorge slopes upward as a glacis, and is swept by 
 the fire of the enceinte. 
 
 515. ..The interior glacis of the demilune commences at the 
 counterscarp of this work, and has a glacis-slope outward, its 
 width being 15 m. Here commences the revetted gorge of 
 the covered-way. The width of the covered-way is 10 m. Its 
 interior crest is an indented line. There are no traverses in 
 this work, unless required for its defilement; 
 
 516... A spacious and strong redoubt is placed in the demi- 
 lune salient place of arms. Its faces are 132?m. long, and re* 
 vetted. Its parapet is thrown back, leaving a corridor in 
 front of it, and is curved at the salient for live guns, sweeping 
 along the capital. A bonnet is placed in its salient to cover 
 the corridor from enfilade, and two traverses for the same ob- 
 ject on its terreplein. This redoubt forms a mask for the por- 
 tion of the demilune occupied by the traverse. 
 
 517...C'homnara places strong redoubts, jf, with revetted 
 scarps and gorges in the reentering place of arms. The para- 
 pets of these works are curved at the salients for batteries to 
 Bweepthe approaches on the bastion capitals and tie- demilune 
 glacis, and they are thrown back from the scarp walls to give 
 a corridor for sharp-shooters. As these redoubts are n< 
 sarily contracted, Choumayi prefers {o them a strong redoubt 
 of larger dimensions, placed in the bastion salient plac* 
 arms, and organized like tin 
 
 5 18.. .One of the most striking features of ChoumaiVa modi- 
 fication-., ie the mode in which he proposes to organize the 
 21 
 
162 CHOUMAKa's MKIIImI). 
 
 • 
 
 large bastions, with defences which shall s*crve as an interior 
 retrenchment in ease the bastion is one of the points of attack J 
 or convert the bastion into an isolated fort, or citadel, for the 
 garrison, in ease the besieger gains possession of the interior 
 of tha enceinte through an assault. This he proposes to ac- 
 complish, b y increasing the lengths of the exterior side, and' 
 also of the bastion Hanks. 
 
 519. ..With this object, Chouinara places a row of easeinates 
 within the bastions, on a line perpendicular to their capitals; 
 Each casemate is from 60 to 80 feet long, from 12 to 20 feet 
 wide, and 12 feet high. This row of casemates serves as a 
 curtain both for the retrenchment of the bastion and for the 
 defence of the gorge against an interior attack. For the de- 
 fence of the salient portion of the bastion, a cut is made across 
 each face and extended to the capital. The scarp of this cut 
 is made into the form of a bastion front with orillons at the 
 shoulder angles ; the casemates forming the curtain of this 
 front. The eounterscarp of the cut may be either revetted or 
 have a simple slf>pe of earth. In the latter case, the bottom 
 of the ditch of the front at the foot of the scarp wall is at a 
 suitable level to admit of a suitable height of scarp wall to 
 secure it from escalade. A broad ramp leads from the, centre 
 casemate, along the capital toward the bastion salient, to the 
 counterscarp of the cut, and there branches into two other 
 ramps, leading up to the bastion terreplein on the right and 
 left. Until the besiegers are about to breach the bastion i'accs, 
 their parapets are left intact, and the portions of the cut along 
 which the parapets, run are filled tip, as in the bastion on the 
 right, thus leaving a free communication throughout the inte- 
 rior of the bastion. So soon as it is thought neeessarj to cut 
 off this communication, and to get the retrenched portion in 
 a state of defence, that portion of tjie parapet across the cuts 
 is demolished, the cut excavated and suitably arranged, and 
 the parapet of the retrenchment formed in part of the earth 
 arising from these changes. The parapet of the front of the 
 retrenchment is thrown back, leaving a corridor for sharp- 
 
 
choumara's MiTiion. 163 
 
 shooters covered by A slight parapet ; that portion of this cor- 
 ridor along the retired Rank being covered by the earthen 
 mask of the orillon. Choumara further proposes, where there 
 is a probability of the scarp of the bastion face, which closes 
 the cut on the exterior, being opened, so that a breach might 
 be made, by firing through it, on the flank of the retrench- 
 ment, to run the scarp wall of the retrenchment at right angles 
 across the cut. as shown on the right faee of the left bastion, 
 and to arrange the bastionnct, which this modification would 
 give at the shoulder angle, for sharpshooters. 
 
 520. ..To expose the interior of the retrenchment to the fire 
 of the flanks of the adjacent bastions, and to the parapet of a 
 second retired interior retrenchment, resting on the two cur- 
 tains adjacent to the bastion, of attack, a portion of the para- 
 pet of the bastion flanks, near the curtain, is demolished, and 
 a slope is given to the portion of the terreplein on which it 
 re-ted. The retired interior retrenchment Choumara proposes 
 to make an earthen-work in the form of a Jiastion'ed front, 
 breaking the faces in the most suitable manner to sweep the 
 rear of the retrenchment in its front. 
 
 •V_'l...The dispositions to convert the bastion into a citadel 
 are similar to the preceding, consisting of a small front, the 
 faces of which are nearly in the prolongations of the adjacent 
 curtains, with oriilons to cover the corridor of tfle retired 
 flank. This front has a covered-way and glacis in advance of 
 it, the crest of which masks the scar]). 
 
 522. ..Choumara has made an ample provision for an easy 
 communication between all points of the enceinte and the out- 
 works, so placing them as to be well covered from the besieg* 
 erjs fire and well swept by that of the garrison — preferring 
 wide ramps for this purpose. The communication from the 
 enceinte with the main ditch is through gate-ways in the scarp 
 wall of the curtain, at its extremities. The ram pari at t ; 
 points is removed to the level of the main ditch ; the portion 
 
 of it between them, along the Centre Of the CUi;taill, being sus- 
 tained at the ends by revetemenl walls run back perpendicu- 
 
lb'-± < ii'H maka's M 1.1 HOD. 
 
 larly to the scarp wall of the curtain. Ramps lead from the 
 gorges of the bastions down to these outlets into the main 
 ditch. From these outlets the communications to the outworks 
 are around the flanks of the tenaille, and through the enceinte 
 ditch, to ramps placed along the enceinte counterscarp Leaning 
 into the demilune, the demilune ditch, the enceinte cov- 
 ered-way, and »its redoubts in the places of arms ; and from 
 the demilune ditch to the redoubt of the demilune salient 
 place of arms. Posterns on flie faces and flanks of the bas- 
 tions, near the shoulder angles, lead to the corridors of the 
 enceinte. Passages are left at the ends of the faces of the 
 outworks, leading from their corridors to the interior of the 
 works. To keep open the communication between the bas- 
 tions, a gallery between their gorges is made along the curtain 
 wall. 
 
 523. ..For the security of the casemates, barricades can be 
 made in their doors and windows, by means of timber let in 
 grooves "made in the walls ; the space between the exterior 
 and interior timber facing being filled with sand-bags. 
 
 524... Rkm auks. The memoirs in which Choumara brought 
 his propositions before the public naturally attracted attention, 
 as much, perhaps, from their polemical character and piquancy 
 of style as their professional interest. They contain but few 
 things, thf germs of which are not to be found in writers who 
 preceded him. His modifications respecting the parapet^ 
 throwing them back from the scarps and breaking them into 
 directions best suited for defence, are to be met with in CKaa- 
 seloxip's propositions. His proposals for lengthening the bas- 
 tion flanks, and occupying the salient places of arms by 
 redoubts with considerable command, are to t)e found in the 
 method of cle la Ohiche. To Virgin he seems to be indebted 
 for his organization of interior retrenchments, which are 
 to convert each bastion into an independent work, equally pro- 
 vided for defence against approaches, both from the interior 
 t and exterior o£ the enceinte. Like disputants, usually of an 
 ardent temperament, he over estimates the value of many of 
 
OBGOTTMASa's Mi.uitUi. lti. r > 
 
 his propositions, and loses sight of their countervailing defects. 
 By laying down as a principle what may be exceptionahly 
 good in practice, he 1ms rather weakened hie own positions. 
 This is the case, particularly, with his. rule of the independence 
 
 of the parapets on the scarps, which, if adopted in all cases, 
 might demand a greatly increased and hurtful command, and 
 cut up to great disadvantage the interior spaces of the bastions. 
 His introduction of the ehemihs de rend on the faces of the 
 bastion and demilune, add realty very little, if at all, to the 
 exterior defence; whilst they contract the interior space of 
 these works, break in upon the unity of the defence, and 
 place the troops in them in a very exposed position to the 
 means of annoyance possessed by the besieger. His expecta- 
 tions with respect to the effect of his fire in the direction of 
 the capitals, in delaying the besieger's approaches up to the 
 third parallel, were hardly warranted by tic experience gained 
 in artillery and small arms, even at the time the last edition 
 of his memoirs appeared. It is hardly to be questioned, now 
 that these weapons have been so greatly improved, both in 
 range and accuracy of fire, that, considering the increased de- 
 velopment of the besieger's parallels, which gives him a choice 
 of positions for his batteries on so extended a line, the concen- 
 trated fire he could bring to bear on the batteries in question 
 would not only soon ruin their casemates, but would greatly 
 damage the adjacent faces, and also the thinks of the bastions, 
 although covered from enfilading views, either by the direc- 
 tion of the parapets of the faces or the high traverses raised 
 with the same Object These advantages in the position of the 
 besieger, it is thought, would prevent any delay in pushing 
 forward his approaches up to the third parallel. After this, 
 the approaches would probably be retarded beyond the usual 
 time allowed in the attack od Cormoritairijme's front, owine 
 chiefly to the redoubts in the bastion ami demilune Balient 
 places of arma ;md the arrangement of the fa r in the 
 
 ditch. 
 
 Supposing an enceinte organized according to his 
 
166 coehorn's method. 
 
 method, and containing interior retrenchments to oppose the 
 besieger's approaches, both from without and within the en- 
 ceinte, (Jhoumara estimates at least six separate epochs of 
 breaching batteries, as follows: 1st, against the redoubt of the 
 demilune salient place of arms; 2d, against the demilune' and 
 the redoubt of the'bastion salient places of arms ; 3d, against 
 the bastions; 4th, against the bastion retrenchment; 5th, 
 against the retired retrenchment ; 6th, and finally, against the 
 bastions converted into citadels by the fronts with which their 
 gorges are closed. According to* the estimate of time made 
 by Choumara, it would re<jutre 112 days from the opening of 
 the trenches to the final assault and reduction of the last de- 
 fences. 
 
 COEHOBJTS METHOD, 
 
 526...Coehorn, a Dutch engineer of great eminence, was the 
 contemporary and rival of Yauban, both in actual warfare and 
 in the engineer's art. Like Yauban, he is the author of sew 
 eral methods, in which he has shown the same preeminent 
 skill as Yauban, in the adaptation of his art to local features, 
 and, perhaps, more originality in his combinations; for Yau- 
 ban rather made use of, and improved upon, the defensive 
 branch of his art, as he found it, than originated: whereas, 
 many of Coehorn's devices are his own. 
 
 527...Coehorn's fronts are arranged with a view to aquatic 
 sites, like those of Holland, where water is found by excavat- 
 ing to the depth of a few feet below the natural surface, by 
 means of which, wet ditches can be combined with those 
 which are dry, so as to procure not only security against a 
 
coehorn's method. 167 
 
 surprise, but, as will be seen further on, to afford facilities for 
 an active defence against the enemy when in possession of the 
 dry ditches. 
 
 528. ..Plan. Coehorn has adopted the mode of laying out 
 the lines of his front, used by some of the earlier engineers; 
 fixing, in the first place, the inferior sides of tlfb space to be' 
 enclosed, taking these lines as the magistrals or exterior lines 
 of the curtains in the bdstfoned system. 
 
 52i>. ..Assuming A B, PI. 15, as the position of the interior 
 side, Coehorn makes its half length, A B, 75 toises, French 
 measure. From A, the same distance, 75 toises, being set off 
 to C, on the capital, or bisecting line of the angle of the poly- 
 gon, gives the salient of ' the exterior side; this side in the 
 hexagon being 224 toises. Bisecting A B, the half, B I), is 
 taken for half the curtain. 
 
 The lines of defence are drawn from the extremities of the 
 curtain, thus determined, to the opposite salients of the ex- 
 terior side. From the salients of the exterior .-id.-, as centres, 
 with the lines of defence as radii, arcs, 1) G, being described, 
 give the faces, C G, of the bastions measured along the lines 
 of defence. 
 
 The portions of the faces thus determined are not revetted 
 toward the ditch; the exterior slopes of their parapets descend- 
 ing below the water level to the bottom of the ditch, as shown 
 on the cross section (i' If. 
 
 530.. .At the shoulder angle of the bastion, Coehorn has 
 placed a stone tower, of which Q I I. K //is the plan. 
 
 An interior elevation of this tower is shown on the section 
 
 Q R. This tower ii arranged on top with a parapet for an 
 
 open defence. It is arranged with bomb-proof arches, and is 
 
 coated on the interior" side, Q II. to Bweep the drv ditch 
 
 between the bastion and the Cavalier within it. 
 
 'I'.. se1 mit the tower, II is drawn perpendicular to <\ 
 and 18 toisee in length; a distance, I. of S^ toit tdken 
 
 on the prolongation of (' C f II I\ is drawn parallel to I. 
 audi toises in length; KL is found by joining A' with the 
 
168 
 
 COEUORN S METHOD. 
 
 c 
 
 opposite salient, making K L equal to 14 toises taken along 
 this line^ the points, 1 and Z, thus determined, are joined by 
 an arc of 60°. 
 
 The curved projecting portion of the tower forms an orillon, 
 which covers the concave flank P D, which is also an arc of 
 60°. • . 
 
 531. ..The faces and flanks of the cavalier have a revetted 
 scarp, as well as the portion I) S of the curtain; which is 
 thrown back on the prolongation of the line of defence, and 
 closes the gorge of the bastion. The magistral of the face of 
 the cavalier is parallel to C G', and -J^.V toises from it. The 
 magistral, S, of the flank is concentric with the one, P D, 
 of the bastion, a ditch 16 toises wid'e being left between the 
 two flanks. 
 
 532. ..The interior of bastion face C Gf which forms the coun- 
 terscarp of the cavalier, is arranged with a loop-holed gallery 
 for sweeping the cavalier ditch. 
 
 533. ..The space between the orillons and curtain is occupied 
 by a tenaille, of which I U T Vis the exterior line at the 
 water level. The point T is on the line of defence, and at 140 
 toises from the salient ; the portion T IT is perpendicular to 
 this line of defence, and the portions / £7 and T V are on the 
 lines of defence. 
 
 534.. .The enceinte ditch is 24 toises wide at the water level. 
 An earthen counterguard, D C\ for musketry defence is placed 
 in front of the bastion. 
 
 535. ..The 6alient, Z, of the demilune is at 93 toises from the 
 point IF, where the enceinte counterscarp cuts the capital of 
 the front ; its demigorge, W £', is 534, toises. The demilune 
 ditch is IS toises wide, and that of the counterguard is 14 
 toises. 
 
 536. ..The demilune contains a small redoubt, the faces of 
 which are revetted, and parallel to those of the deinilune. The 
 ditch of the redoubt is dry, and 16 toises wide. A curvilinear 
 space is formed at the gorge of the redoubt, to afford a covered 
 harbor for boats used for communication. A small capon- 
 
t coehokn's method. • 169 • 
 
 mere, in the form of a lunette, is placed at the gorge of the re- 
 doubt to seenre the retreat of the troops from it to the boats. 
 The walls of this caponniere are pierced with two tiers of loop- 
 holes ; the work being divided into two stories, the lower be- 
 ing covered with heavy beams and earth to resist shells, the 
 upper being uncovered. 
 
 537.. .A similarly covered caponniere, of a rectangular shape, 
 for one tier of fire, is placed across the ditch of the redoubt, 
 near its extremity. A small -wet ditch is placed in front of 
 this work, and is flanked by a counterscarp gallery under the 
 portion of the demilune face opposite to it. 
 
 53S...A like construction, of a pentagonal form, is placed 
 within the salient angle of the demilune, the faces of which, 
 toward the interior of this work, arc loop-holed to sweep the 
 ditch of the redoubt and the interior of the demilune. 
 
 539.. .The covered-ways of the counterguard and demilune 
 are 13 toises wide ; a reentering place of arms is formed at the 
 junction of the two, the faces of which are 30 toises. 
 
 54<>...A redoubt of a quadrangular shape, the faces *>f which 
 are respectively 12 and 15 toises, and which is a simple loop- 
 holed wall, closes, in connection with two traverses, the gorge 
 of the reentering place of arms. 
 
 541. ..A gallery, covered with heavy timber and earth, is 
 placed f> toises in advance of the reentering place of arms, to 
 furnish a fire of musketry to sweep the glacis in front. 
 
 One of the most prominent features in Coehorn s method is 
 the combination of wet and dry ditches, with a view to secur- 
 ity from surprise, and for protracting the defence and disput- 
 ing the ]m of every point foot by foot. For these purr 
 - the wet ditches are made M-ry wide and contain water, 
 at Least six feet in depth, thus forcing the enemy to the con- 
 struction of long dikes to effect their passage ; whilst the bot- 
 ,toin of the dry ditches uoe kept slightly above the general 
 water level, so a> to compel th«' enemy to bring the earth, as 
 well as the other materials r< quisite for their passage, from 
 other points. In addition to these purely passive mea.is, the 
 
170 coehorn's method. 
 
 dry ditches are organized for an active defence by sorties, and 
 are well swept by direct and reverse fires from casemates, 
 counterscarp galleries and oaponnieres. The portion of the 
 dry ditch between the faces of the cavalier and bastion is swept 
 by artillery in the casemates under the orillon, and by two 
 pieces behind a wall pierced with embrasures, which closes the 
 space between the shoulder angle, 0, of the cavalier, and the 
 extremity, JI K, of the orillon. In like manner, the ditch be- 
 tween the flanks is swept from casemates under the portion S 
 D of the curtain. A reverse fire of musketry sweeps .the ditch 
 along the face, from counterscarp galleries under the bastion 
 faces, and from a gallery along the capital, which serves as a 
 communication between these galleries and the interior. 
 
 To cut off the communication between the ditch of the face 
 and flank, a wet ditch is made in front of the orillon and the 
 connecting wall. This ditch is flanked by the counterscarp 
 gallery. Two drawbridges over this ditch form a means for 
 sorties on the enemy whilst effecting the passage of the ditch 
 of the face. A drawbridge for a like purpose is thrown over 
 the wet ditch, in front of the caponniere in the ditch of the 
 demilune redoubt. Besides these provisions for carrying on 
 what the French well express by une guerre de chicane, Coe- 
 liorn makes a profuse use of palisadings in all parts of his 
 front where an obstinate stand is to be made, besides employ- 
 ing countermines to destroy such parts as, being in the enemy's 
 possession, would be prejudicial to the defence. 
 
 542.. .The question may very naturally be here asked, to 
 what extent such means of defence may be depended upon ? 
 The answer is, only so far as they can be kept in a good con- 
 dition for the moment when they can be brought into play. 
 With the present improved practice of artillery there is little 
 doubt but that all of these means for the ditch defences, as 
 rovided by Coehorn, except the counterscarp galleries, would 
 e destroyed by the ricochet fire of the enemy's enfilading 
 batteries at an early period of the siege, the masonry of the 
 loop-holed redoubts and caponnieres being altogether too 
 
coehorn's method. 171 
 
 slight to withstand the effects of this fire. Could these means 
 be kept in a good condition, we have the warrant of numerous 
 sieges in favor of their efficacy in the Jiands of an intelligent 
 and resolute garrison. 
 
 543... Profiles. In the plan and profiles the horizontal 
 plane of site is assumed at 24 feet above the plane of compari- 
 son. From an examination of the references on the figures of 
 the plate, the relief and relative command of all the works are 
 readily deduced. It will be seen, on examining the plan, that 
 a portion of the bastion face, adjoining the salient, is raised 3 
 feet higher than the portion toward the orillon, thus forming a 
 bonnctte, which not onlv gives a greater command to this por- 
 tion, but masks more effectually the ditch and fhasonry of the 
 cavalier. A like arrangement is seen in the demilune face, 
 both at the salient and toward the gorge, and with a like view 
 to mask the caponniere and the loop-holed redoubt in the 
 salient of the demilune. 
 
 544... Remarks. It will be seen, on reference to the plan 
 and sections, that Coehorn has given but a slight command to 
 all his works — his object in this being economy, and to depend 
 rather upon the near titan the distant defence, his dispositions 
 having been made almost exclusively for the former. The 
 command of the crest of the covered- way is only 44, feet over 
 the natural site, the terreplein of this work, which is 74; feet be- 
 low the crest, being thus placed a little above the water level, 
 with a view to compel the besiegers to bring the earth and 
 materiel from a distance to form a cover for his approaches in 
 the covered-way. 
 
 545. ..The only dispositions for the distant defence by artillery 
 are in the cavalier and demilune redoubt, except in the dry 
 ditches, where gun.- and mortars might be placed to fire over 
 the low parapets of the exterior works. 
 
 546...Beaides the exposure to ricoehel caused by this slight 
 Command, the directions given to all the faces of the works arc 
 rery favorable to the enemy's enfilading batteries. 
 
 547. ..The dimensions of the parapet of the counterguurd. 
 
172 TENAILLKD SYRTKM. 
 
 which serves as a mask for the triple flank fire of the cavalier, 
 bastion and tenaille, and those of the parapets of the bastion 
 and demilune, which se/ve as face covers" for the cavalier and 
 demilune redoubt, are insufficient for these purposes, as they 
 could readily be opened "by shells fired horizontally into them, 
 or by small mines, and expose the scarp of the interior works 
 to the enemy's breach batteries on the glacis. The scarp 
 walls, moreover, of the works in question, are not of sufficient 
 height to secure them from an open assault. The only feature, 
 then, of the ingenious combinations of this celebrated engineer, 
 which would find an application in the present state of the art, 
 is the combination of wet and dry ditches for sites similar to 
 those for which his dispositions were designed. 
 
 TENAILLED SYSTEM. 
 
 548. ..Several engineers, of professional eminence, have pro- 
 posed tenailled enceintes, as offering defensive properties su- 
 perior to bastioned enceintes. This system has found but few 
 advocates ; and, except in particular localities, where the na- 
 tural features of the site demanded it, and for small works, it 
 has met with no practical applications. 
 
 549. ..Requiring that the salient angles shall not be less than 
 60°, and the reentering angles between 90° and 100°, the 
 tenailled system is only adapted to regular polygons/of a suffi- 
 cient number of sides to admit of these conditions being satis- 
 fied. If the exterior sides are kept within the limits usually 
 admitted by engineers for bastioned enceintes, the faces of the 
 tenailles become very long and the reenterings very deep ; 
 thus presenting two serious defects : long lines which are very 
 
CARNOT S TKNAILLED 1METH0D. 173 
 
 f 
 
 much exposed to enfilade, and a great diminution of the inte- 
 rior space as compared with the bastioned enceinte. The 
 ditches when dry can only be swept by casemated defences»in 
 the reentering angles; and even then but partially, unless the 
 casemate embrasures are placed very mar the level of the bot- 
 tom of the ditch, in which case the enceinte would be exposed 
 to a surprise through the embrasures ; and, in the contrary 
 case, liable to a like attempt from the dead space at the re- 
 enterings below the embrasures. In wet ditches this exposure 
 to surprise would be much less if the ditches could not be 
 forded. In either case the defect arising from embrasure case- 
 mates placed in the reentering angle, would be a serious ob- 
 jection to using the guns of each side simultaneously. When 
 the salient angles of the tenailles are acute, the effect of the 
 enfilading fire would not be felt alone on the face enfiladed, 
 but upon the adjacent face in front, and shot passing over 
 would damage the adjacent tenailles. 
 
 The foregoing are the chief objections to this system. It 
 presents no advantage but the very illusory one, considering 
 the consequences arising from it, of long faces presenting a 
 mutual flanking and cross fire ojf considerable extent. 
 
 CARNOT' S TENAILLED METHOD. 
 
 550. ..The great reputation acquired by Carnot during the 
 French revolution, in which lie played so eonspicuotiB a part 
 MB a soldier, statesman and executive officer, connected with 
 his professional education as an engineer officer, gav$ for a 
 
 time a certain j>r<*li<je to his views on fortification, which 
 
174 CARNOt's TENAILLED JIETHOD. 
 
 I 
 caused them to be adopted in Germany, where they have been 
 applied in some of the works constructed since 1815. 
 
 £51. ..Struck with the exposed state of the artillery, on ram- 
 parts without bomb-proof shelters, to ricochet fires, and the 
 feeble resistance offered by garrisons in some of the* sieges of 
 his day, particularly in an active defence by sorties, Carnot 
 seems to have considered the weakness attributed to existing 
 fortifications to the want of such shelters, and also of such 
 means of communication with the exterior which would ena- 
 ble the garrison to sally out in force and assail the trenches 
 of the besiegers. 
 
 552.. .The systems of defence which he has proposed are de- 
 vised to remedy these two prominent defects, and consist in 
 providing a number of casemates, on suitable points of the 
 defences, from which a constant shower of small projectiles 
 and hollow shot can be brought upon the besieger's works ; 
 and, instead of the revetted counterscarp, which constitutes 
 one of the main securities against a surprise — but as ordinarily 
 arranged is an obstacle in the way of throwing rapidly for- 
 ward a considerable body of troops from the interior to oper- 
 ate on the exterior — he proposes to form an earthen one with 
 so slight a slope that troops can ascend it with ease to make 
 sorties ; the ordinary covered-way and glacis being also done 
 away with to facilitate these operations. 
 
 553. ..Carnot, in his published works, has given his views 
 upon the ameliorations of which the fortifications of his time 
 were susceptible, besides some new combinations for a bas- 
 tioned system and two tenailled systems for aquatic and irreg- 
 ular sites, in which the defects of this latter system are less 
 objectionable, and to which they can J3e more easily applied. 
 
 554.. .Plan. This consists of a continuous enceinte, PL 16, 
 Pig. 2, formed of tenailles, the reentering angles of which are 
 90°, and the salient angles not less than 60°. The interior of 
 the place is enclosed by a wall, A, of sufficient height to be 
 secure from escalade ; the plan of it is a tenailled line, with 
 reentering angles of 90° and salients of 60° ; it is arranged with 
 
carnot's tenailled method. 175 
 
 two tier* of loop-holes for musketry, which arc within arched 
 recesses in the wall, of sufficient depth to screen the men serv- 
 ing them from vertical fire. Casemated batteries, Q, for artil- 
 lery, are placed at the reenterings, to flank the ditch between 
 the wall and tlie earthen rampart of the enceinte. This wall 
 serves the same. end as the one in Montalembert's method. 
 The salients, A A, are about 250 yards apart. 
 
 555. ..The rampart and parapet of the body of the place, O, 
 are detached from, the scar]) wall in front, a narrow corridor 
 being left between the foot of the exterior slope and the bach 
 of the wall. The wall is arranged like the interior one, with 
 one tier only of loop-holes for musketry fire. At its reentering 
 it is broken forward and is pierced with embrasures, to form a 
 position, TF, for cannon to flank the ditch between it and the 
 tenaille. 
 
 550. ..The tenaille, G, masks the greater portion of the scarp 
 of the body of the place, its wings being about 120 yards in 
 length ; it is closed by a detached wall with loop-holes. 
 
 557. ..From the reentering of the tenaille a double caponniere 
 of earth leads by a ramp to an earthen redoubt, A*, placed at 
 the reentering formed by the counterscarps. This redoubt is 
 intended to hold troops in readiness for sorties, and is without 
 a ditch, so that they can move out over its parapet' 
 
 558. ..Earthen conntergnards, the salients of which, B B, are 
 about 390 yards apart, mask the walls of the bodv of the place 
 and the tenaille; sufficient space only being left between their 
 extremities, I 1 ] F, and the caponniere for the circulation 
 through the ditches. This work, like the tenaille, has a narrow 
 terreplein, and is intended only for a defence of musketry, ex- 
 cept at the salient portions, which, like the salients of the en- 
 ceinte, are. arranged t'<>r artillery to fire in the direction of 
 their capitals from behind blindages or calcinated traverses. 
 
 The foot of the parapet, M .1/, of the reddnbt is placed 40 
 yards within the line joining II II. 
 
 55H...PK"! ii.k. The positions of the different lines on the 
 plan are readily ascertained from the. section on ■/ 1\\ Fig. 9, 
 
176 POLYGONAL SYSTEM. 
 
 as the lilies are all parallel. The relief and the relative com- 
 mand of the different parts are also given on the same section. 
 560.. .Remarks. The expectations of Carnot with respect to 
 the efficacy of the proposed shower of small projectiles upon 
 the trenches of the besiegers, from the casemates for mortars 
 and howitzers, have been shown from experiments as not likely 
 to be realized. From similar experiments, the detached scarp 
 walls proposed by him would soon be overthrown by a heavy 
 curvated iire, which might be brought to bear upon them over 
 their earthen masks. The ditches and terrepleins of all the 
 parts of his tenailled method are peculiarly exposed to rico- 
 chet fire, whilst the long wings of the tenaille and the double 
 caponniere mask, to a great degree, the fire of the enceinte 
 along the ditches. The provision made for sorties from there- 
 doubt at the reentering of the earthen inclined counterscarps 
 is exceeding^ feeble, and it is not easy to see what would 
 prevent an active enemy, on the repulse of a sortie, from fol- 
 lowing the retreating troops into the works themselves, or, 
 having driven them into the ditches, from regaining their 
 trenches with comparatively little loss. 
 
 POLYGONAL SYSTEM. 
 
 561. ..The polygonal system has been proposed by several 
 engineers of distinction, but its most ardent advocate has been 
 the celebrated Montalembert, whose views have been, more or 
 less, carried out in many of the more recent constructions of 
 the engineers of Germany. 
 
 Consisting of either a simple polygonal enceinte without re- 
 enterings, the sides of which are flanked by casemated capon- 
 
POLYGONAL SYSTEM. 177 
 
 niercs, placed at the middle point of the fronts; or of fronts 
 either slightly tonailled, or of a bastioned form, with short 
 casemated flanks to flank the faces of the central caponniercs. 
 this system affords more interior space, and, from the mode 
 adopted for flanking the enceinte, will admit of much larger 
 fronts than either the bastioned or the tonailled systems. The 
 salient angles, moreover, will be more open in this than in the 
 other two systems. From these peculiarities of this system, 
 the positions suitable for the erection of batteries to enfilade 
 the faces of the enceinte are less advantageous, from their 
 being thrown in nearer to the adjacent fronts, than in either 
 of the other systems; whilst a greater development of trenches 
 will also be requisite to envelop the fronts of attack. These 
 obvious advantages, however, are more than counterbalanced 
 by the want of the concentrated cross fires which are afforded, 
 in both the bastioned and tenailled systems, in advance of the 
 salients of the enceinte, and upon the ground generally in ad- 
 vance of the fronts. Each front of the polygonal system 
 offers, moreover, a long and vulnerable line to enfilading and 
 slant fire, which will also, to some extent, take effect on the 
 reverse of the adjacefit fronts. Bnt the chief objection to this 
 system lies in the mode adopted for flanking the enceinte. 
 The casemated capnnniores fof this purpose being exterior to 
 the enceinte, it will be exposed t<> escalade as soon as the fire 
 of the caponniercs is silenced, which, considering the structure 
 of the caponniere, and the exposure of its embrasures to the 
 enfilading batteries, will, in all probability, take place at an 
 early period after this fire is opened. 
 
178 MONTALKMBEBTfi POLYGONAL METHOD. 
 
 MO.XTALKMUEKT'S POLYGONAL METHOD. 
 
 r.«'.^ — \ nit .nir the writers on permanent fortification wh< 
 works have had an importaut beariug on the progress of the 
 art, Montaleinbert holds a conspicuous place, although not 
 educated as an engineer. Struck by the evident defects of the 
 methods of his predecessors, particularly the want of c 
 mates, both for defensive dispositions for artillery and mus* 
 ketry and the shelter of tin- garrison and munitions, Montalem- 
 oerl devoted his time, talents and fortune, to bringing about a 
 change in the direction in which it seemed to him called tor. 
 His efforts, however^ led to no modifications of consequence 
 during his life (which was principally spent in angry contro- 
 versies with his opponents), except the extension of casemated 
 defence.- Cor sea-coast works; and it is only within a compar&t 
 lively H-ccnt period, since the termination of the great wars in 
 Europe, in the present century, thai a new school of engineers 
 has grown Jtp in < ierinany, based upon the views put forth 
 mainly by Montalemhert ; and that these views have met with 
 iavor in other parts, although still opposed by many aide en- 
 gineers, in all countries, who contesl their soundness. 
 
 563.. .The principal propositions of Montalemhert consist in 
 the entire rejection of the bastioned system as, according bo 
 his views, unsuitable to a good defensive disposition; and in 
 its steiad he proposed to ule either the tenailled system or the 
 polygonat system ; in basing the Btrength of these last systems 
 upon an overwhelming force of artillery fire in defensive case- 
 mates, and in organizing Btrong permanent works within and 
 independent of the body of the place,' which are to serve as a 
 secure retreat for the garrison when forced to give up 'its 
 defence. 
 
 564.;. M" t of the objections urged against the bastioned 
 
montalembert's polygonal method. 1 7!» 
 
 SysteM and its outworks haVing al ready hecn adverted to in 
 the analysis of the front, it will lie unnecessary to recap! tulate 
 them here; arid as the teuaflled Bystem, Composed of faces of 
 equal lengths, with reentering angles of t0° and salient ang 
 6f 60*, and termeil by Montalemhert pt ,-j>< wdifn il.tr forfijica- 
 timi, from the position of the faces at the reentering*, lias 
 many obvious and mora serious defects than either of the 
 other two; it is proposed to give here a description of the 
 polygonal system alone, and that in its most simple form; the 
 one in which Ifontalembert presented it for the fortifications 
 at Cherbourg, one of the most important naval stations in 
 France. 
 
 56.">...Montaletnhert first gave the name polygonal system to 
 a trace of the, enceinte in which all of the angles are either 
 salient, or where the reenterings are very alight The distinc- 
 tive of his method are shown in the works which he 
 projected for the defence of the harbor of Cherbourg. 
 
 In tine tract' proposed for this places .\' }'. Fig. 
 1. PL 16, ifl the exterior side, or direction of the scarp. The 
 body «»f the place consists of the scarp wall, I), Fig. 1, and 
 
 on on /' <j, arranged with oasesnates for artillery and 
 
 Bketry; of a corridor, (7, between these casemates and the* 
 
 en rampart and parapet, //. In rear of the rampart ii a 
 
 high wall, A. arranged with loop-holes, within which the gar* 
 
 rison retires when driven from the defence of the rampart. 
 
 :...< lasemai ed caponnieres, .V. which are secure from a 
 coupdi mam, are placed along the rampart, and so arrai 
 that a fire can be thrown from them over the parapet, and 
 
 along the terreplein. The conidor, < . is also -wept by I 
 
 mated caponniere, 6-', for musketry, and the tVont of the 
 wall, A . by a lil -it. 
 
 :pal caponniere for hanJcing the main ditch 
 
 i- in the fom of a lunette, and i .: the middle of the 
 
 ■ 
 the flanks, //. and t A . ol fab 
 
 ! with two 1 artillery and musketry fire, 
 
l v " Mi'MAI.I M!:J IM*s POLYGONAL Mi:nit>l>. 
 
 each flunk carrying ten pins, and each face twelve guvs. A 
 wet ditch, A separates the faces and flanks; a loop-holed wall 
 encloses the portion between the Hanks, from which the oppoi 
 site portion between the faces is swept by musketry. 
 
 569.. .The caponniere is covered in front by a face oov.er, A', 
 od earth in the shape of a redan. The scarp of the enceinte is 
 etiveped in Like manner, by the continuous face cover, 0, of 
 earth) in the reentering afaglea of which, caseniatcd 1 «at t . 
 ol two stories, for artillery and musketry, are placed to flank 
 the ditches, and sweep the positions for counter-batteries 
 around the salients of the covered-way. These batteries are 
 masked in front by the earthen works, <S and Q. The whole 
 is covered by the covered-way, arranged in the usual manner. 
 
 The better to flank the main caponniere, the portion of the 
 caseniatcd gallery joining it is arranged with two tiers of artil- 
 lery fire, the remaining portion having but one tier of gabs. 
 
 570...Pbobtlbb, The sections along J 3 Q, R S, and T U, 
 show the relative eoiiiniand of the different works, and the 
 width of the ditches and earthen ramparts. 
 
 The coimnunieatioiis between the different works are by 
 bridges across the wet ditches. . 
 
 • 571. ..It is now admitted on all bands that, although Mon- 
 talembert has rendered important services to the progres 
 fortification, particularly as regards the more extensive em- 
 ployment of caseniatcd defences, still, many of his projects 
 were visionary. How far the recent works constructed in Eu- 
 rope, which are based on his views, will answer their ends, 
 remains to be seen by the test of actual siege operations against 
 them. 
 
 The partisans for and against these views are equally confi- 
 dent in their arguments ; but with the rapid improvement in 
 artillery which has taken place within the last few years, and 
 the heavier calibre which will doubtless be hereafter used ill 
 siege operation, it is very doubtful whether, from what expe- 
 rience has already shown as to the effects of artillery on case 
 mate defences, they will be found to withstand these powerful 
 
L'IMM i, I l.'MAN FORTIFICATIONS. 181 
 
 means, in which case the systems based upon Montalembert'l 
 view must fall to the ground. 
 
 RECENT GERMAN FORTIFICATIONS. 
 
 5T2..Jj3 the large additions made to the fortifications of the 
 German States since the general peace in Europe in 1815, the 
 man engineers have, for the most part. <>f these new struc- 
 tures, embraced the ideas put forth in the works of Montalem- 
 hert and Carnot, adopting lor the plan of their enceintes the 
 polygonal system with flanking capomtieres, communing with 
 these numerous casemates for defence, for bomb-proof shelters, 
 for quartering the troops, and preserving the munitions and 
 other Ston S. 
 
 573... From what has l»een published on this subject l>y the 
 G rman engineers themselves and other BSuvopean Writers, the 
 following appear to be the leading feature.- upon which these 
 work.- are based : 
 
 Let, To occupy the principal assailable points of the position 
 to be fortified, by works whicb shall contain within them- 
 all the resources for a > defence l>y their garrit 
 
 the~e works being placed in reciprocal defensive relations with 
 
 that the tailing of one ,,f them 
 into the :l neither oompel the loss of the. 
 
 others oor the surrender of the position. 
 
 k j«l. To cover the space to the rear of these ind< 
 works, cither by a continuous usually of the poly- 
 
 -tern, with -.i 'licient I 
 
 core it from escalade : the parts of tl com- 
 
 bined with the indep< tidem 
 the icli, both during the i distant de- 
 
L81 KI.MNT oIKMW Fc'KTini'ATIi'N-. 
 
 fence, shall be Bwepl in the most effective manner by their 
 fire; or else to connect these works by long curtains ; or, final- 
 ly, t<» employ these works, as in a system of detached works, 
 cither to occupy important point;- in advance of the main work 
 or for forming capacious entrenched camps with a view to the 
 tnalities of a war.* 
 
 3d. To provide the most ample means for an active defence 
 by covered-ways strongly organized with casemated redoubt*) 
 and with spacious communications between them ami the in- 
 terior for soi-ties in large bodies. 
 
 4th. So tx> organize the artillery tor the near defence that it 
 shall he superior to that of the besiegers at the same epoch} 
 and lie placed in positions where it will be sheltered from the 
 besieger's guns up to the time that it is to be brought into 
 play. 
 
 574-...PlAjST ; The plan of the independent works may be of 
 any polygonal figure which is best adapted to the part as- 
 signed them in the defence of the position; but they are gen- 
 erally in the form of lunettes, PI. 23, Fig. 2, having a revetted 
 scarp and counterscarp to secure them from escalade. In the 
 gOrge of the work a casemated defensive barrack is placed, 
 which serves as a reduit or keep; a simple loop-holed wall, 
 which is flanked by the barrack, closing the space between it 
 and the thinks ot the work, and securing the latter from an assaidt 
 in the rear. The ditches of the work art' either flanked from 
 the enceinte in their rear, or, when the work is a detached 
 one, by oaponnieres, or counterscarp galleries. The work is 
 Usually organized with a covered-way, having one or more 
 ea.-ematcd redoubts, and a system of mines both tor the exte- 
 rior and interior defence. 
 
 575. ..The barrack is usually arranged for two or three tiers 
 of covered fire, ami an upper one, with an ordinary parapet 
 and tenvplein, on which the guns are uncovered and destined 
 for the distant defence. The two upper tiers of covered tire 
 are for artfllery, to sweep the interior of the work, and to 
 reach, by curvated tires, the approaches on the exterior. The 
 
 
utiM <;: i:man hiktti-k IATIOKB. 183 
 
 lower tier is loop-holed for musketry to sweep the Interior, 
 The barrack is surrounded by a narrow ditch on tin- interior, 
 and this, when accessary, is flanked by small caponni&res 
 placed in it, which are entered from the lowest story; The 
 barrack communicates with the interior by a door at some 
 
 suitable point: and the coniniunication between the interior 
 of the work and the exterior is through doors in the wall en- 
 closing the gorge. 
 
 5'7G... Considerable diversity is shown in the profiles of th 
 works. They usually consist of a parapet and rampart, of 
 ordinary dimensions, for the uncovered defence; of scarps 
 either partly detached and loop. holed, with a corridor between 
 them and the parapet; or of scarps with relieving arches ar- 
 ranged with loop-holes for musketry; or .of a combination of 
 these two. The height of the barrack, and the command of 
 the paTapei of the exterior work are. so determined that the 
 masonry of the former Bhall be perfectly covered from the 
 direct lire of artillery, and the exterior be perfectly' swept by 
 the artillery of the work. The portions of the counterscarps 
 at the salients are also arranged with defensive galleries to 
 sweep the ditchei — usually with musketry, but in some cases 
 with artillery. 
 
 r»77... In the salient angles of the work casemates are ar- 
 ranged tor mortars, to fire in the direction of : the capitals : and 
 one or more easemated traverses are placed on the terreplein, 
 to obtain a fire on the exterior and to cover the terreplein 
 from ricochet. The masonry of these traverses is masked by 
 the parapet. 
 
 rns lead from the interior of the work to the 
 ;> galleries, the corridors, the ditch capoanieres and the 
 mated mortar battery in the salient. 
 
 579.. .The Bystem of mines for the exterior defence coi 
 simply of listening galleries leading outward from the oounter- 
 rp gallerii 8. That for interior defence is similarly ar- 
 ranged; the communications 'with it being either from the 
 barrack caponnien - or from the counterscarp of its ditch. 
 
580... The work is provided with powder magazines, which 
 arc placed at the points of the interior least exposed t<> the 
 enemy's fire; and covered gaard-rooms, store+rooms for mining 
 tools, etc., are made in connection with the posterns. 
 
 5S1 ... Pi:' ii- ir.i s. Tn the profiles of their works, the German 
 engineers follow nearly the Bame rules for the formB and 
 dimensions of their parapets as those in general use in other 
 services. They employ three kinds of scarp reveteraeuts : 1st, 
 the Ordinary full revebement, PI. 20, Fig. 1, or sustaining 
 wall, with counter-forts^ 2d, reveteraents with relieving arches, 
 PL 21) Figs. 1, 2, cither with or without defensive dispositions, 
 as circuni-tances may demand; 3d, Bcarp walls, either partly 
 or wholly detached from the rampart and parapet. In all of 
 these cases, they give to their scarp walls a height from 27 to 
 30 feet for important works, and about L5 feet for those less 
 so. The hatter of these walls is usually one base to twelve 
 perpendicular. For the full revetement with counter-forts, 
 thev regulate the dimensions of both so as to afford the same 
 stability as in the revetements of Tauban. 
 
 582. ..In their reyeteinents with simple relieving arches, they 
 use either one or two tiers of arehes ; placing the single tier 
 either near the top or toward the middle of the wall, according 
 to the nature of the soil and the pressure to be sustained. 
 
 58o... Revetements with relieving arehes for defence, or scarp 
 
 galleries, are arranged for one or two tiers of fire. The back 
 of the gallery is sometimes left open', the earth falling in the 
 natural slope in the rear ; or it is enclosed either with a plane 
 Of a cylindrical wall, according to the pressure to be sustained. 
 584... When the upper part of the wall is detached, PL 20, 
 Fig. 7, to form a corridor between it and the parapet in its 
 rear, the top portion alone is, in some cases, arranged with 
 loop-holes and arcades, or with recesses to their rear, to cover 
 the men from .-hells: in others, a scarp gallery is made below 
 the floor of the corridor to give two tiers of fire. The corri- 
 dors are from 8 to 20 feet in width, and when deemed requisite! 
 
Ki:< 1 \ 1 oIKM \N 1 oktifK'ATIONS. 1 s "» 
 
 they are divided, from distance to distance, by transverse loop* 
 holed traverse walls for defence. 
 
 585. ..When the scarp calls' are entirely detached, PI. 20, 
 Figs. 4, 5, 0, they are arranged for either one or two tiers of 
 fire, with arcades to cover the men ; the banquette-tread of the 
 upper tier of loop-holes resting on the arches of the lower tier 
 of arcad 
 
 586. ..The counterscarps are revetted, cither with the ordinary 
 wall, or arranged with a defensive gallery, with a full centre 
 arch, parallel to the face of the Counterscarp wall. 
 
 -7. ..The German engineers make a liberal use of bomb- 
 proof casemates for mortar and gun batteries. The former are 
 either placed in the rear of the parapet, or of the rampart, and 
 along the faces, or else in a salient angle. In the former i 
 they are cov< red in front by the parapet, in the latter either 
 by the scarp wall alone or by a easemated defensive ma.^k 
 placed in front of the battery. When placed alon^ a face, PI. 
 •J". Fig. '.», they are arranged for one or several mortars, and 
 frequently with two tiers of arches, the upper one for the - 
 vice of the mortar and the lower one for a bomb-proof shelter 
 for troops or munitions. The chamber occupied by each mor- 
 tar is a rectangle, L2 feet wide, and about 20 feet in depth; 
 this i^ covered by a full centre mmparl arch, the height of the 
 piers at the back of the chamber being -1 feet, and in front from 
 
 o' to !< feet above tin; level of the mortar platform. This ena- 
 ble- the -1,. d t,. clear the top of the parapet in trout, which i.> 
 about 12 feel above the level of the platform, and 21 feet in 
 front of the battery. The chamber is, in some easeB, hit open 
 
 both in front and rear, to allow the smoke to escape readily 
 and to diminish the effect of the concussion of the discharge on 
 the masonry; in other cases it Is closed by a wall in the rear — 
 an opening being left in this wall, immediately under the 
 arch, tor the same purpose. A -mall ditch is placed in front 
 of the batten ; and the wall in front L£ extendi d about .'; 
 above the platform, I r the in< n from the i 
 
 - that may fall into the ditch. The abutments ot 
 H 
 
L86 KHIM GSSKAfi ImKUKKATIONS. 
 
 arches are 7 feet thick, and the piera -1 feet. The arches are 9 
 feet 6 inches thick ; they are covered on top by from 4 to ''< 
 feet in thickness of earth.; and. in Like manner, the arch and 
 abutment are secured «>n the side exposed to an enfilading fire* 
 An ordinary traverse is placed on the same side, to cover the 
 masonry ami communication between the front of the battery 
 and the parapet ; the chambers <>f the mortars are entered from 
 the front, or from the sheltered side, by a door in the abut- 
 ment. . 
 
 588.. ."When placed in an obtuse salient, PI. 21, Figs. •'•. 1. 
 behind a scarp with a corridor, a space of 10 or 12 feet is left 
 between the back of the scarp wall and the front of the bat- 
 tery. The platfbrms of the mortars are about the same distance 
 below the top of the scarp. The arches are covered by tho 
 earth of the parapet, to the depth of 5 or 6. feet. The dimen- 
 sions and arrangement of the chambers and arches are the 
 same in this as in the preceding case. The communication 
 from the interior of the work to the battery is by a postern, 'I 
 feet'in width. ■ A casemated guard-room is made in connection 
 with the postern ; and when the scarp is arranged with reliev- 
 ing arches, either for defence, or tbr other purposes, an arched 
 stairway is in some cases made as a communication from the 
 postern to the casemates. A transverse wall with a door-way, 
 serves to cut off the court in front of the battery from the cor- 
 ridor to the rear of the wall. 
 
 5S9... In the less obtuse salients, the front of the battery is 
 made circular ; the chambers being so placed that the fire of the 
 mortars can be thrown in the direction of the capital. A case- 
 mated defensive traverse, placed in the salient, masks the bat- 
 tery in front, and it is covered on the flanks by the earth on 
 the top of the arches. The details, otherwise, are the same as 
 in the preceding ease. 
 
 590.. .In the arrangement of casemated traverses for guns. 
 PI. 20, Figs. 10, 11, 12, the chamber for each gun is a reOH 
 tangle, 24 feet in depth, estimated from the interior crest of 
 the parapet, and 12 feet wide. The chamber is covered by. a 
 
RECK NT ol.KMAN K( (IM'IKK A HOSTS. 187 
 
 full centre arch, the height from the level .if the platform to 
 the crown of the arch heing S£ feet. The arch is 2 feet thick, 
 the piers between the arches 3 feet, and the abutments ;> >i feet. 
 The mask wall in front of the chamber is 3 feet thick. This 
 wall is covered in front by the parapet, ami by several layers 
 of fascines or of heavy timber, laid across the embrasure in 
 the para] iet and above the one through the mask wall. The 
 cheeks of the em braaure in the parapet are likewise revetted 
 with heavy timber, to some distance in front of the mask wall. 
 The masonry is covered on top and on the sides with 5 or 8 
 feet thickness of earth, to secure it from shells and enfilading 
 shot. The casemates are left open to the rear. 
 
 &l...In some cases, a blinded battery for a single gun, PI. 
 20, Fig. 12, is arranged by enclosing the sides and front of the 
 chamber with wails, and covering it with a layer of heavy- 
 timber, BUpporting two thicknesses of large fascines, covered 
 with a thickness of 5 or 6 feet of earth. The dimensions of 
 the chamber are the same as in the preceding ease. 
 
 592 M ,Xhe caponnieres, IM. 21, Figs. s . :*. L0, fortflanking the 
 main ditch. 'usually consist of two faces and two caseinated 
 Hank batteries of two stories each ; the lower story being 
 loop-holed for musketry and the upper pierced for artillery. 
 Each battery consists of several rectangular chambers, each 
 
 chamber for a single gun being 1 -J feet wide and 24 feet deep, 
 
 or of smaller dim i, according to the cali5*e of the gun 
 
 and the kind of i on which it is mounted. The upper 
 
 chambers are covered with bomb-proof arches, the lower one 
 by arches of sufficient strength tor the weight thrown upon 
 
 them. The front mask wall of the es is <i feel thick; 
 
 the wall in rear is 3 feet thick, and is pierced with wind 
 for light and ventilation. Openings for the escape of the 
 .e arc also make in the front nia.-k wall, immediately be- 
 low the crown- of the arches. An interior court 80 feet in 
 width is left between tl Lank batfc d when the 
 
 batteries are d< tached from the scarp wail, t: 
 
1 88 Kl 01 N 1 i.IKMAN 1 OETIFIOATK 
 
 is enclosed by a loop-holed wall built on each si<lo in the pro- 
 longation of tin- front mask wall. 
 
 593. ..The face- <>f the caponniere form a salient of 00°. 
 They are separated from the flanks by two stories of arched 
 corridors, in front of which arc two arched chambers of two 
 stories, the upper chamber being arranged for mortars. An 
 open triangular court is left between the front walls of these 
 chambers and the faces of the caponniere. The upper part of 
 the walls of the faces, along. this court, arc arranged with ar- 
 cades and loop-holed for musketry, ami have an open corridor in 
 their rear on the same level as the chambers of the second 
 story. 
 
 594.. .The caponniere is provided with a power magazine find 
 other necessary conveniences for the defence. 
 
 595.. .The flanks of the caponniere and its interior are BWept 
 by the musketry of the scarp galleries in it* rear. The faces 
 in like manner are swept by artillery and musketry in ca.-e- 
 mates behind the scarp. 
 
 The arched chambers of the upper story arc covered by a 
 thickness of 5 or 6 feet of earth. 
 
 596...Caponnieres of smaller dimensions, termed hastiormets^ 
 PI. 22, Fig. 1, placed at the angles* of redoubts to flank the 
 ditches, are usually arranged for mnsketvv, but sometimes re- 
 ceive artillery. Those for flanking the ditches of the indepen-* 
 dent works iitffulvance of the enceinte are sometimes placed 
 in the ditches of these works, sometimes behind the scarp wall 
 of the enceinte, and sometimes in casemates in the main ditch, 
 detached from the scar}) wall. 
 
 597. ..The communications from the interior with thecapon- 
 nieres are by posterns. 
 
 598. ..The defensive barracks, PI. 21, Figs. G, 7, forms one of 
 the most distinctive features in the organization of the Ger- 
 man fortifications. The plan of these -works may lie of any 
 figure to suit the object to be subserved by them. When 
 placed in the gorge of an independent work and serving as a 
 keep to it, their plan is usually semicircular. 
 
BBCEBTT (;r,i:MAN F0BTIFICATI0N8. 189 
 
 599. ..The barrack consists of one or two stories of arc-hod 
 ehatnbers for covered fire and an open battery on top, with an 
 earthen parapel and terrepleim 
 
 600...The arched chambers arc formed by connecting the 
 front and rear walls of the barrack by transversal walls, which 
 serve as piers for the arches of the ceiling, the soffits of which 
 arc either cylindrical or conoidal, according as the piers are 
 parallel or otherwise The chambers are about 18 to 20 feet 
 wide and 60 feel in depth ; their height, under the. crown of 
 the arch, from 9 to 11 feet. The arch of the highest chamber 
 is 2-£ feet thick, and, being covered with a capping and the 
 earth of the open battery on top, is bomb-proof; the arches of 
 the lower stories are 1 .1 feet thick. The front wall of the bar- 
 rack is usually 6 feet, and is pierced in each chamber with one 
 embrasure and two loop-boles. The rear wall is 3 feet thick, 
 and has a window in each chamber for light and ventilation. 
 Openings for ventilation are also made in the front wall, just 
 beneath the crowns of the arches. Door-ways are made 
 through the transversal walls to form a communication between 
 all the chandlers. These are sometimes placed along the cen- 
 tre of the piers, at others near their extremities, so that the 
 chambers being divided by slight partitions into two compart- 
 ments, for the quartering <«f the troops, there will be a contin- 
 uous hall either along the centre or near the rear wall, upon 
 which all the apartments open. The barrack! are. other? 
 arranged with all the requisites for lodging the troopt comfort- 
 ably and healthfully. The lower story of the barrack is sur- 
 rounded by a narrow ditch, A drawbridge across this ditch 
 ires the entrance to the barrack at the 
 
 OOlt.Jn some cases, PI. 21, Fig. .">. where the front wall of 
 the barrack is much exposed to the besi< fire, thep 
 
 made thicker oear the»froat wall ; and they each have two 
 vertical grooves to n seive timber, laid horizontally, betw< 
 which sand) b* packed in to afford shelter when 
 
 front wall has become much damaged by tin rtil- 
 
 lel'Y. 
 
190 FRONTS OF P081 
 
 602r..The foregoing summary description, with the plates, 
 will give a good general ides of the principal defensive* a*- 
 rangement8, constructed of masonry, which enter »o largely 
 into the recenl German fortifications, and upon the details of 
 which tlic German engineers have bestowed great attention. 
 
 608... The adoption of the polygonal system, with capouniere 
 defences for the main ditch, lias enabled the ( German dngineeji 
 to give, in their fortifications, a greater exterio* Bide than in 
 the bastioaed system generally, and still admit of lines of »h'- 
 fence in which grape, canister and small arms, particularly 
 tlic later improved musket, will tell with efficacy upon the 
 besieger's works on the glacis around the salients of the en- 
 ceinte. With a few exceptions, nothing of a very reliable 
 character has heen published as to the trace of these works, 
 further than the general defensive dispositions. From these it 
 appeals that, keeping in view the cardinal point in all fortifi- 
 cation, the adaptation of the various fronts to the site of the 
 work, so that all the approaches upon them shall be com- 
 nianded and swept by their tires, whilst the principal lines of 
 the enceinte receive the best direction to place them as little 
 as possible* within the range of enfilading positions, the exte- 
 rior side is usually kept somewhere between 400 and 000 
 French metres, or between 450 and 700 yards. 
 
 FRONTS OF T0SEN. 
 
 604...The following is an outline of 4hc trace and defensive 
 dispositions of a front of the fortifications of Posen, one of the 
 most noted of these recent structures. The exterior side, A 
 
FRONTS OF POB] ». 101 
 
 B, PI. 22, Fig. 2, is 580 yards; B distance, CY>=1-15 vl A', 
 is set off on the perpendicular of the front and within it; and 
 on the line joining the salients, *-l, A*, with F. distances, A IT, 
 B J/, equal !-<» A /!. being set off '/wr the faces of the front. 
 The salient, A', of the independent work is on the pcrpeu- 
 dieular of the front, and at a distance from £7 espial to ^ A />'. 
 Describing from A' an are with a radius of 20 yards, aild draw- 
 ing tangents, to it from the joints //"and M. gives the counter* 
 scarps of the independent work J the feces, A" F. A' F\ are 
 parallel to the counterscarp, and equal to\AB. The ditches 
 <>t' this work are flanked by casemated caponnieres, ///, J/iV, 
 which arc 35 yards in length, or sufficient for four guns. The 
 directions of tlu »e flanking casemates being nearly perpendicu- 
 lar to the directum of the faces A/ /•'. E F. The flanks, F <.\ 
 F <r\ receive the most snitahle directions for sweeping the ap- 
 pro aches in advance of the salients of the front. The main 
 ditch is about 30 yards wide, its counterscarp being parallel to 
 the faces of the enceinte, and the gorge of the independent 
 Work is on the prolongation of this counterscarp. The cur- 
 tains of the enceinte are directed from the points A V. on the 
 
 point (\ and are thus nearly parallel to the exterior side. The 
 main ditch is flanked by a la: natedV defensive barrack, 
 
 having three stories of covered lire, the lower for musketry 
 and the upper for artillery, and an open battery on top. The 
 plan of this work is that of the letter F: the circular partpro- 
 jects within the independent work, and * its keep ; 
 
 side.- are nearly perpendicular to the faces of the enceinte and 
 are prolonged within the enceinte, serving as a defensive capon- 
 niere to Hank the main ditch, to sweep the terrepleins of the 
 enceinte curtains, and also the interior, within the ran- 
 
 the guns of two round sowers with which th< ■•• term!- 
 
 Mb d. The Bides of the barrack are separated from the ram- 
 part of the curtain by lateral ditches 1<> yard.- wide. Which 
 
 to the main ditch from the interior for troops 
 large bodi< - for sorties. 1 I of the • I ' 
 
 - thrown hack from the scarp, leaving ■ corridor 
 
102 PSOITIS "I POSES. 
 
 • 
 
 twees the foot of its exterior slope and the BCarp wall, the 
 floor of which i.- L2 feel above the bottom «>t' the main ditch. 
 The scarp wall rises 1''- feci above the level of the floor, thus 
 giving it a total height of B8 feet above the bottom of the 
 main ditch. This wall is loop-holed for small arms. The 
 counterscarp wall of the main ditch is 24 feet in height. The 
 faces and thinks of the enceinte have a relief of 41 feet; the 
 relief of the curtain being only 4ft feet. ' The corj-idors of the 
 curtain terminate at the court or open space behind the think- 
 ing easejnatcs, 7/7, M N. Posterns lead from the interior to 
 the corridors of the faces and Hanks, and from the lateral 
 ditches to the corridors of the curtain. The interior open 
 space between the sides of the defensive barrack is closed by. 
 a loop-holed wall between the end towers. \ ditch surrounds 
 the towers and the gorge between them, across which a bridge, 
 terminated at the wall by a draw, gives access to the interior 
 open space and the barracks. 
 
 605. ..The scarp, rampart and parapet, PI. 22, Fig. 5, of the 
 independent work, are arranged with a profile similar to that 
 of the enceinte. The circular portion of the defensive barrack 
 which serves as the keep, is surrounded by a ditch, "which is 
 swept by small capoiinicres attached to the keep. A circular 
 mortar battery, covered in front by a casemated traverse, is 
 placed in the angle of this work, and behind this a casemated 
 battery for howitzers is placed on its terreplein, in the direction 
 of its capital, to give reverse views on the glacis of the col- 
 lateral independent works. The gorge of this work is closed 
 by a loop-holed wall which extends between the keep and the 
 scarp wall of the flanks. The communication between the 
 main ditch and the interior is through a gate-way in this wall. 
 Posterns lead from the interior to the corridors of the faces 
 and flanks, and to the mortar battery in the salient. 
 
 r»oi;...The counterscarp of the independent work is arranged 
 
 with a defensive gallery, with which a system of mines tor the 
 
 ■rior defence is connected. A system of mines for the in- 
 
I'OKI AI.I.X ANDl-.K. lit.'; 
 
 terior defence is connected with the small caponnieres in the 
 ditch of the keep. 
 
 607. ..The covered-way is without the usmal traverses, its in- 
 terior crest being broken into a cremaillere line. Its salient 
 ami reentering places of arms are occupied by casemated re- 
 douhts. The communications from the main ditch to the 
 covered-way are by wide ramps, which are at the gorges of 
 the reentering places of arms, and under the tire of theii 
 redoubts. 
 
 FORT ALEXANDER. 
 
 60d...Among the most reliable of the traces published of 
 German fortification, is that of the main front of Fort Alex- 
 ander, a detached quadrilateral work of the fortification.- c£ 
 Coblents, gives in the description of these fortifications by 
 • Humphrey. 
 
 609...Plaj6*. The exterior sides of the enceinte of this fort, 
 1M. 22, I nn a parallelogram, the acute angles of which 
 
 are v -"> . The main and rear front- arc each 500 yards, and 
 the other two 420 yards each. The main front is of the poly- 
 .1 .system, with a strong defensive caponniere to flank the 
 main ditch. The caponniere is covered by a demilune, and 
 th^ salients of the enceinta by counter-guards ; the ditch 
 these works being flanked by casemated batl 
 
 ring formed between them. There is no covered-way hi 
 front of these outwork-, their counterscarps beii tilth, 
 
 with a gentle slop.'. \ small earthen work, containing a i 
 mated redoubt, is thrown up at the salients of the counter' 
 guard counterscarp. 
 25 
 
 
194 FORT ALEXANDER. 
 
 610. ..To construct the trace, take a 5=500 yards, for the ex- 
 terior side of the enpeinte, which divide- into three equal parts, 
 a d=d e=eb. Bisect a h by a perpendicular, on winch sot off 
 h JI=/< d=h e=l-6 a b. Through //, drawing a parallel to a 
 b, and setting off along it the distances 11 A = H Z?sbS20 
 yards, the points A and B will be the salients of the counter- 
 guards. 
 
 611. ..From //as a centre, with the radii lid, He, describe 
 two arcs, on which set off from d and e the chords, d i=e k~ 
 33 yards, these will be the lengths* of the ca.semated flanks; i 
 k being joined, gives the enceinte curtain. The salient angle 
 of the main caponniere is constructed by drawing, from a 
 point, m, on the capital, at a distance of 20 yards from the 
 lines, lid, He, lines to the extremities, i and It, of the case- 
 mated flanks. The flanks of the caponniere, t n=v o, extend 
 back to the exterior side, and are 33 yards in length and 33 
 yards apart, or each 16£ yards on each side of the capital. 
 The faces of the counterguards are directed on a point, C=i 
 A B—$?>\ yards on the capital from //. The salient, F, of 
 the demilune is 1-6 A i?=106 yards from the point C; its 
 faces, F D, F E, arc parallel to the lines II d, II e, which 
 last, joined by an arc of a circle, described from m as a centre, 
 with a radius of 20 yards, and terminated at the counterscarp 
 of the enceinte ditch, which is 28 yards from a b, will give the 
 demilune gorge. A casemated battery for three guns, behind 
 the demilune scarp wall, flanks the couhterguard ditch, and 
 one for three guns flanks the demilune ditch, and closes the 
 opening between the demilune and counterguard at this point. 
 A narrow ditch, 10 feet wide, is left between the flank of this 
 battery and the extremity of the counterguard, as a communi- 
 cation between the main ditch and the ditches of the outworks. 
 This opening is masked by an overlap of the counterguard. 
 
 612. ..Casemated, or blinded batteries^ are made in the sa- 
 lients of the enceinte and of the demilune. 
 
 613.. .Profiles. The main caponniere, Fig. 8, has two tiers 
 of covered artillery fire on the flanks, of Ave guns each ; the 
 
FORT AI/KXAXDKU. 105 
 
 lower to sweep the main ditch, the upper the terrepleins of the 
 counterguards ; its faces have two tiers of loop-holes. It has 
 no uncovered fire, but a simple covering of earth as a bomb- 
 proof. 
 
 614.. .Casemates, for five mortars each, are placed in the sa- 
 lients of the enceinte, at the foot of the rampart slope. 
 
 615... A narrow corridor, Fig. 0, the floor of which is 20 feet 
 above the bottom of the main ditch, is left behind the scarp wall 
 of the enceinte; the faces and curtains of this wall are loop- 
 holed, and arranged with arcades to shelter the men, like the 
 detached scarp walls of Carnot. These scarps arc 30 feet high. 
 The command of the enceinte over the parade is 26 feet. 
 
 616. ..The scarp walls of the demilune and counterguards, 
 Fig. 7, are arranged Like those of the enceinte. The command 
 of these works is 16 feet. Their counterscarps are arranged 
 with loop-holed galleries, from which communications lead to 
 a system of mines for exterior and interior defence. 
 
 617.. .The rear side of this fort, not being exposed to artillery, 
 is simply closed by a loop-holed wall and ditch. A large, cir- 
 cular, defensive barrack occupies the centre of this rear front, 
 serving as a keep to {he fort, and to sweep by its fire the 
 ground on the rear and flanks of the front. 
 
 618. ..It will be seen that, in the arrangement of the plan of 
 tliis work, the polygonal system, with caponniere defences, of 
 Montalembert, has been adopted as the basis, with such modi- 
 fications as the features of the site afforded, t<> withdraw the 
 principal Lines from the range of the enfilading views from 
 without. 
 
 A 
 
li'fi WORK AT GERMEE8HBTM. 
 
 . WORK AT GERMERSIIEIM. 
 
 G19...In tlie organization of works with wet ditches, the Ger- 
 man engineers adopt the same general disposition of the ele- 
 ments of a front as they do in dry ditches; occupying the moat 
 important points of the polygon to be enclosed by independent 
 Works, and composing the enceinte of fronts of the polygonal 
 system? taking their exterior sides between the limits of 350 
 and 050 yards, and sweeping the main ditch, and the positions 
 for the besieger's breaching batteries around the salients of the 
 enceinte, by the flanks of a defensive caponniere. The follow- 
 ing concise description of a front of the teU <l< pont opposite 
 Germersheim, will give a good idea Of the general defensive 
 arrangements in such eases. 
 
 02O...Plan. The front, X Y, PL 33^ Fig. 1, is a tenailled 
 line with a slight reentering at the centre of the exterior side. 
 The salients of the front are occupied by small bastions, with a 
 scarp gallery on the faces and thinks, and having its gorge 
 closed by a loop-holed wall, with a defensive, casemated reduit 
 at its centre. 
 
 621. ..The centre of the front is occupied by a capacious case- 
 mated edifice, which extends from the interior of the gorge of 
 the independent work, across the main ditch, to within the 
 enceinte. The circular portion of this edifice, jwithin the inde* 
 pendent work, has two tiers of covered fire, with an open bat- 
 tery on top, and serves as the reduit of this work. The central 
 portion has two tiers of covered fire, and serves as a caponniere 
 for sweeping the main ditch, etc. Underneath this portion are 
 arched passages, to communicate by water between the ditch 
 on each side of the caponniere. The part of the edifice within 
 the enceinte is a defensive barrack, with three tiers of covered 
 
WOIJK AT OKKMKKSUKTM. 197 
 
 fire, and an open battery on top, from which the terreplein of 
 the enceinte curtain, the gorges of the bastions and the glacis 
 of tfie enceinte can be swept. 
 
 622. ..The enceinte curtain is not revetted with masonry. 
 The exterior slope of its parapet descends to a wide berm .»<v- 
 eral feet above the water level of the wet ditch, and which, in 
 many places, is planted with a thorn thickset hedge as an ol>- 
 Btacle to an assault. The rampart of the curtain is* sustained 
 within by a high wall, which joins the loop-holed walls of the 
 bastion gorg< s, and is flanked by the baBtibn reauits. 
 
 623.. .The independent work is ip the form of a lunette; its 
 faces being divided into three parts, each with a greater com- 
 mand than the oneain its rear. The profile of this work is like 
 that of the enceinte curtain ; its ditches are dry. their bottoms 
 being slightly above the water level of the main ditch. The 
 ditches are flanked by casemated caponnieres which extend 
 across them to the goTges of the reentering places of arms, for 
 which works they al>o serve as reduits. They are connected 
 with the central rednit by loop-holed walls. 
 
 oi'4...The covered-ways are without .traverses. A casemated 
 reduit or traverse separates the reentering place.- bf arms, on 
 each side, from the coVered-ways bf the enceinte and independ- 
 ent work, and sweeps them both. These are connected by 
 loop-holed walls in front, which join those in their rear. 
 
 625. ..The counterscarps of the enceinte and independent 
 
 work are of earth. 
 
 626.. .A passage leads from the interior across the main ditch 
 on each sid< • ■' tl • central casemated edifice, and extends along 
 the counterscarp of the enceinte. This passage is a few 
 above the water level, the two ends being connected by brid< 
 across that portion of the main ditch where the arched Com- 
 munication under the main caponnien 
 
 \ ept by two small, casemated caponn iiich pro 
 
 from the - d. - of the main caponni 
 
 7...Iiani].s lead from the . to the inte- 
 
1 98 WOBK at (.1 i:m;:k-iii.im. 
 
 rior of the independent work at its gorge, and to that of the. 
 reentering places of arm* 
 
 628.. .An interior ami exterior system of mines is connected 
 with the independent work and the r&duita of the reentering 
 
 place ft' an. 
 
 0:2!'... In the application of this system to wet ditches., the 
 means of. communication between the enceinte and the various 
 
 outworks, .by the passages and small bridges, across the main 
 ditch and along the sides of the central caponniere, are princi- 
 pally npticeable, as the other features do not differ in any great 
 degree from its application to dry ditches. Here, one of the 
 main objections to wet ditches, the difficulty of keeping open a 
 communication by means of rafts or boats, for sorties and other 
 purposes, is obviated by the arrangement of the passage in 
 question. The bridges, connecting the break in this passage, 
 may be so arranged as to be readily removed or destroyed 
 when the besieger has gained such a footing beyond the main 
 ditch as, by a rapid assault) to endanger the* safety oi' the en- 
 ceinte. This mode, however, of establishing a foot communi- 
 cation between the enceinte and the outworks of a front, is not 
 peculiar to this system ; as like means are used in the bastioned 
 system, by placing the bottom of the double caponniere slightly 
 above the water level of the main ditch, connecting the two 
 parts of this ditch, on each side of the caponniere, by a narrow 
 ditch, between this and the gorge of the demilune redoubt, 
 over which a slight temporary bridge is thrown, so long as it 
 is found necessary to keep open this communication. 
 
 630.. .The German engineers apply the preceding dispositions 
 to every class of detached works, whether within reach of the 
 artillery of the main work or beyond it. In the former case, 
 the work is either in the form of a lunette or a redan, accord- 
 ing to the requirements of the site, the gorge of the work being 
 secured by a slight, loop-holed wall that can be readily de- 
 stroyed by the artillery of the place, and thus open its, interior 
 to view when occupied by the besieger. In the latter, the 
 plan is that of a polygonal redoubt enclosed on all sides by a 
 
WORK AT GKKMIKSlll IM. 109 
 
 parapet. The ditches in nil such cases are flanked by small 
 osponnieres, placed at the angles of the work, and arranged 
 
 both for musketry and artillery, besides a counterscarp gal- 
 lery, which serves as the point 6f departure tor the galleries of 
 the exterior system of mines. 
 
 631. ..Remarks. The apparently wide divergence beweCn 
 the German fort in' ration of the present day and the bastioned 
 system, which lasl had been adopted as the normal one thrdugh- 
 out the world until these innovations were practically intro- 
 duced, has given rise to active discussions among engineers in 
 Europe, in which, as in all such cases, very ultra ground has 
 been taken by both parties to the dispute. In each system the 
 points admitted as GBsential in all fortification of a permanent 
 character are sought for, viz: lsfy an enceinte secure from es- 
 calade and thoroughly flanked by artillery and small arms ; 
 2d, Mich an adaptation of the plan of. the enceinte to the site 
 as shall secure, as fill as practicable, the principal lines from 
 enfilading views ; .'Id, outworks of sufficient strength in them- 
 selves, and of such defensive relations to the enceinte, as to 
 force th :• to carry them by regular approaches before 
 
 being able to assault the enceinte; 4th. interior defensive 
 works, or keeps within the assailable points of the enceinte, 
 and in the outworks first Subject to an attack, to give confi- 
 dence to their garrisons in holding out to the last extremity; 
 r>tli. the means necessary for an active defence* 6th, the use of 
 mines as an auxiliary : 7th, the protection of all masonry by 
 earthen masks from the distant batteries of thi 
 
 J. ..The only question then is. by which of these two ■ 
 
 terns the object in view ' I attained. Tn the solution of 
 
 . we are nut at the outset by the ;t b- any 
 
 reliable teste as to the real value of t 1 (op- 
 
 ted in th< G Noplace fortified by thi.- mode 
 
 subjected to . and nothing can. t ; 
 
 be with certainty stated a- to the degn e i the pe- 
 
 culiar d- lopted may I ted to at 
 
 ■ some experiments made at "Woolwich, England, some 
 
200 WORK A I ci KM! B8HXDC. 
 
 years ago, to test the practicability of breaching detached 
 scarps, uke those of Cannot, when covered by an earthen mask, 
 with heavy guns throwing their projectiles, within the usual 
 range of ricochet fire, over the earthen mask to reach the wall 
 covered by it; and others made at Bapaune, France, on the 
 effects of shptondef -. Kiese experiments* to- 
 
 isr with Bome facts dmwn from the sieges in Italy and 
 Spain* during the period between the first French revolution 
 and the peace of L815, and the more recent attacks on fortifi- 
 cations during tlie straggle, between Russia and the Allies, go 
 
 to .-how thai all structures of masonry, whenever they can he 
 reached by heavy projectiles within the range of 800 to L,000 
 yard.-, whether in view or not, may be greatly damaged it* not 
 entirely ruined; and that troops within defensive casemates 
 exposed to such a fire, would be soon driven out of them hv 
 thc embrasure shots, and the cannon destroyed. Thai the 
 flanking cappnniereja of the enceinte and of the independent. 
 works in the German .systems are thus exposed and liable to 
 these objections, does not admit of a question. Like assertions 
 may he made of the scarps, which are either wholly or partly 
 detached, and of the traverse walls by which the corridors of 
 the enceinte are divided tor defence. The defensive harracks 
 in the gorges of the independent works, and which serve as 
 their reduits, as well as the loop-holed wall by which the gor- 
 ges of these works are closed, being thrown back from the 
 cover of their parapets, are also similarly exposed. The Ger- 
 man engineers, it is said, have, by the dispositions made in 
 some of their more recent structures, by abandoning the conn- 
 tersloping glacis of Carnpt and his detached scarps, employing 
 in their stead, on fronts of attack, scarps with relieving arches, 
 and covering, to some extent, their ditch caponniere defei 
 by earthen masks, shown some distrust of the methods mostly 
 nsed in their firs! structures, planned upon the views of Mon- 
 talemhert and Carnot. 
 
 633. ..The polygonal trace, which obtains in most of the re- 
 cent German works, has certain prominent advantages and 
 
WORK ai <. u:\ii k-iium. 'Jul 
 
 defects which may be seen bv a slight comparison with the 
 bastion. m1 system. As the exterior sides are longer/land the 
 reenterings of the enceinte less deep than in' the bastioned 
 systems, it billows: l.-t, that the interior space enclosed bv the 
 eaceinte is greater in the polygonal trace; 2d, that the face- of 
 the enceinte arc less exposed to ricochet from the greater ob- 
 tuseness of the salient angles; 3d, that the fire of the faces 
 have thus a better bearing on the distant defence; 4th, that, 
 requiring fewer fronts on a given extent of line to be fortified, 
 there will be fewer flanks and more artillery, therefore) di>- 
 posable for the faces and curtains; 5th, that, in the asnal 
 mode of attack, the besiegers will be forced into a greater 
 development of trenches for the same number of fronts. Such 
 are the advantages inherent in this trace. 
 
 '!.'U...It> defects are; 1st, that the enceinte 1 having no other 
 flanking defence than the main caponniere, it will be exposed 
 to an escalade SO SOOD as the tire bf this defence is silenced; 
 id, that tin- progress of the b . during the last and most 
 
 important period of the - but little delayed, owing to 
 
 the slighter reenterings formed bv the independent works in 
 front of the enceinte salients. 
 
 ...,'IJli" defects in the bastioned trace, and the modes pro- 
 
 d by different engineers to remedy them, particularly 
 tlo ..-'• of Qaxo and Ohoumara, have been sufficiently dwelt 
 Upon to show that, with the advantages inherent in this 1 
 of preserving the means of flanking the enceinte ditch to the 
 last, of throwing the bastion salient- into deep reenteri 
 giving a belter direction to the enceinte faces for sweeping the 
 
 ind in advance of the demilune salient ptible of 
 
 iving all the mean- of casemated defences, of a greal 
 velopment of flank tire, of defensive arrangements of mines, of 
 ample communications tor an active defence, and an extension 
 of the exterior side, fortified comrat nsnrate with the impn 
 late years i:i artillery and -mall arm>. 
 
 ••"....In t Ich have taken place UDOD 
 
 its of these two tra 
 
202 1. 1 KM AX FOKTS. 
 
 rival schools, each has seemed disposed to exaggerate the de- 
 fects and to depreciate the advantages of the system analyzed* 
 and has conducted his mode of attack accordingly. The true 
 point, however, as to the inherent merits of the question, does 
 not lie in a comparison of the means of resistance of a bas- 
 tioned trace, with defective communications and without case- 
 mated defences and mines, ami that of the German sv.-tem, 
 but between the former, with these additions, now regarded 
 by engineers of every school as indispensable to a vigorous de- 
 fence against the greatly improved means of attack of the pre- 
 sent day, and the latter. 
 
 637. ..The fragility of masonry, and the case with which it 
 can be ruined by distant batteries of heavy calibre, particu- 
 larly when pierced with embrasures and loop-holes, like the 
 .caseinated caponnieres and defensive barracks of the Ger- 
 man system, must naturally incline engineers to limit its em- 
 ployment as much as possible, reserving its use for positions 
 where it will not be subject to this exposure, or where it can 
 be so covered with an earthen mask that nothing may be ap- 
 prehended from the besieger's heavy guns. 
 
 GERMAN TOUTS. 
 
 638. ..In their detached works, or isolated forts, the German 
 engineers follow the same defensive measures as in the inde- 
 pendent Avorks belonging to a continuous enceinte. A strong, 
 casemated barrack, PI. 33, Fig. 2, the plan of which is either 
 curvilinear or polygonal, with several tiers of lire, serves as 
 the reduit or keep of the work, and is placed either within it 
 or at its gorge, according to the position to be occupied. The 
 
GERMAN FORTS. 203 
 
 inferior is provided with casemates for guns and mortars, 
 placed at the salients and along the terreplein — frequently 
 under traverses, when these are used to cover a face from en- 
 filading views. The scarp walls are usually built with reliev- 
 ing arches, defensive scarp galleries, and open corridors be- 
 hind the ap per part of the Boarp wall, which is also loop-holed. 
 The ditches are flanked by small capon nie res, placed at the 
 angles of the work, or along its faces, and by loop-holed coun- 
 terscarp galleries; and mines for exterior and interior defence 
 are connected with these galleries and with a ditch which 
 usually surrounds the keep. 
 
 639. ..Tower Fobts. The favor with which the views of 
 Montalemhert have been received in Germany, lias led to the 
 adoption of his circular casemated towers, both as isolated 
 forts and combined in a system of detached Works for covering 
 a ^pace to their rear for an entrenched camp, as at lints. 
 These towers, in their interior arrangements, are the same as 
 the defensive barrack already describe*!, with the exception of 
 those differences in the details of the construction which the 
 difference in their plans would call for. They have several 
 tiers of covered fire for artillery and musketry, and an open 
 battery on top, the parapet of which is either of earth or of 
 masonry, according to the dimensions of the tower. In the 
 
 towers at Lintz they are surrounded by a ditch, and the whole 
 
 of the masonry which would be exposed to the bes bat- 
 
 teries is covered by a glacis, leaving only the guns on top to 
 have direct view- on these batteries, the second tier firing 
 under an elevation over the crest of the glacis mask. The 
 ditch toward the interior is crossed by a temporary fixed 
 a drawbridge leading to the second Btoryfof the tower. The 
 gun.- of the top battery are placed on a revolving platform, 
 their carriages being of a peculiar construction, t<. admit of 
 the axes of the guna remaining paralh not to have their 
 
 shot div< Tge from tl bjecl to he reached, aid. tme 
 
 tim< . ,py as little spaa . la! rally, a- will j for 
 
 the service of the guns. An earthen para the guna 
 
204 TIIK ADAPTATION OF I'lKMANlNT FOBUFIOATIOS 
 
 on the side exposed to the besieger's fire, and one of masonry 
 toward tlif interior. These towers, with'the exception of the 
 open battery, have the defects of divergent fires, common to 
 all works with a circular plan; and the open battery is liable 
 to be rendered useless, or be rained by a well-aimed shot or 
 two, or a heavy shell felling on its platform. The tower-with- 
 out earthen masks can only be used with advantage in j 
 tions where it will not be exposed to being breached from a 
 distance, and is a rery good auxiliary in sea-coast defence, for 
 points where the ohject is solely to prevent an enemy's Vi 
 from making use of a safe anchorage on the coast. 
 
 THE ADAPTATION OF PERMANENT FORTIFICATION TO THE 
 TOPOGRAPHICAL FEATURES OF FRONTIERS. 
 
 640.. .No state, in the present condition of civilization, can 
 be regarded as secure from foreign military aggression, the ac- 
 cessible points of whose frontiers are not occupied by perms* 
 nent fortifications of such strength as shall prevent an enemy 
 from obtaining possession of them by a sudden assault, and 
 thus procuring the means of penetrating into the interior. 
 Guided by the experience of centuries of wars, and the daily 
 increasing facilities which the improvement.- in the materiel of 
 armies and their transportation afford for rapid and powerful 
 offensive operations, the ruling states of continental Europe 
 have, within the last quarter of a century, not only made every 
 effort to place their frontiers in an unassailable condition, but 
 also their great centres of population and wealth in the in- 
 terior, beyond the chances of a sudden attack from an enemy 
 
TO TIIE TOPOGRAPHICAL FEATUEKS <>l FIMN'I TEES. 205 
 
 who might force his way through tlic frontier defences, and 
 march rapidly upon them, thus making these positions the 
 rallying-pointa whore a defeated army can find a safe resting- 
 place, until it can be reorganized and sufficiently strengthened 
 t<> resume the offensive. Such seems to be the result "at which 
 the generals and statesmen of Europe have arrived, after the 
 most mature and careful consideration of the important prob* 
 lcm of national defence, during which the utility of permanent 
 fortifications was seriously called in question by some who 
 pointed, in support of their views, to the very inefficient part 
 the great number of fortified places had played in the wars 
 Waged by Napoleon, when, hy means of overwhelming num- 
 bers, he was enabled to disregard such places, the garrisons of 
 which were too feeble to make any efficient offensive move- 
 ments, until the defeat of his adversary, in one or more great 
 pitched battles, necessarily also threw them into his possession. 
 <•}]. ..In view of the arguments bated on these events, the 
 opinions of Napoleon himself should carry great weight In 
 speaking of the bearing of permanent fortifications in a defen- 
 sive war. he says: "If fortresses can neither secure a victory 
 nor arrest the progress of a conquering enemy, they can at 
 leas! retard it. and thus give to the offensive the means 
 gaining time, a most important advantage in all warfare*." 
 
 In like manner, the Axohduke Charles, of Austria, who showed 
 
 himself one of the ablest adversaries with whom Napoleon 
 had to cope, takes the ground: "That a defensive warfare can- 
 not be systematically and successfully carried on in a country 
 which is not provided with fortresses that have been planned 
 and distributed according to strategical requirements." lake 
 views were held hy the Duke of Wellington, and it is proba- 
 ble that no great general, from the earliest period of military 
 op-, ral own to tl tit moment, I 
 
 the contrary. Without going further hack than the t> 
 contests which have taken place in Kurop.- within 
 years, we gather tin 
 
 We find, on t; Sorts of powerful 
 
206 Tin: adaptation of pbbmaitknt forttftcatios 
 
 Russian forces paralyzed by the obstinate defence of a few 
 weak fortresses, and, in some cases, of simple field-works by 
 the Turks; on the other, the gigantic armaments, by sea and 
 land, of France and England combined, held at bay in the 
 East, and in the Black Sea; and. more lately, the career of 
 of France arrested in the very flush of victory, by the time 
 which it must necessarily have cost her to break down the 
 barriers which Austria had placed in her way in the strong- 
 holds of Northern Italy. The only question, then, on this 
 Subject that remains for solution by a state is in what way 
 such a means of security from aggression can be best adapted 
 tn its own geographical) political and military status. 
 
 642.. .In a country like our own, with so vast an extent >■[' 
 sea-coast and inland frontier, and with political and social in- 
 stitutions which are so antagonistic to every approach to the 
 maintenance of a large standing army as a measure of national 
 safety, this question is one of peculiar importance, both from 
 the open character of this extensive frontier, and from the al* 
 mosl incredible facility with which, as in the late struggles in 
 Europe, and in the contests of China and India, considerable 
 armies, with all their materiel, can be concentrated on distant 
 points by the aid of steam, 
 
 64o...The want of military means of some of our immediate 
 neighbors, and the daily increasing mutual commercial inter- 
 ests between us and the greatest naval power of the world, 
 from whom alone we have any serious danger to apprehend 
 along our inland frontier, would seem to favor the hope that 
 the day may never arrive in Which our country will have to 
 provide against invasion except along the sea-coast; and we 
 may, therefore, dismiss from our consideration any further 
 provision against this eventuality than the security of our prin- 
 cipal harbors, naval stations and commercial marts from a 
 naval attack, or from one combined with the descent of a land 
 force, which last, from the great resources of our country in 
 men and ••means, would hardly attempt to penetrate inland be- 
 yond one or two marches. 
 
TO THE TOPOGRAPHICAL FEATUBE8 OF FRONTIERS. 207 
 
 644.. .Tn the organization of the frontier fortifications of a 
 state, the points to be chiefly regarded are the principal ave- 
 nues of access to the interior, and the topographical features of 
 the frontiers, as they lend themselves, more #r less, to 
 strengthen artificial defences. In conducting an invasion 
 across ao inland frontier, the march of the enemy must nei 
 sarilv be along the roads that intersect it, as these afford the 
 only good avenues for transporting the materiel, etc, of the 
 army. The joints, therefore, or places in their neighborhood, 
 where the principal roads or other avenues of communication 
 erosa the frontier, particularly those which lead to the greal 
 centres of population and wealth, are the ones which neces* 
 sarilv require permanent defences. No absolute rule can be 
 laid down for the distribution or the strength of such works. 
 
 rything must depend upon the more or less of facilitv pre* 
 sented to an enemy for penetrating at one point rather than 
 another, and of the ulterior advantages which the possession 
 of one may present to him over another. 
 
 6 !•'».. .Rivers and mountain ranges are the natural fortifica- 
 tions of states, and. where they form the frontiers, they greatly 
 facilitate the application of artificial defensive means, as they 
 present but few, and those, in general, important points of ac- 
 cess. When the points bf communication on a river are forti- 
 fied, an invading force, however powerful, cannot, without 
 ross the river before first gaining p n of 
 
 them; for, even should a sufficient detachment be left to ob- 
 
 e and blockade the fortresses, the main army, in case of 
 ' r any disaster, might be placid in bj extremely criti- 
 cal position, in its movements to recross the river, with I 
 garrisons of the fortresses threatening its flanks and rear. In 
 offensive operations, fortresses upon a river frontier form i 
 of t! • . an army. If a river in- 
 
 • lie frontier, the point where it rr 
 in its vicinity, should he occupied by a p I work. 
 
 Among such points. I i ccdiarly he 
 
208 THK ADAPTATION OF PERMANENT FORTIFICATION 
 
 held where a river, forming the frontier, is intersected by an- 
 other navigable one "which lies wholly within the frontier. 
 
 646. ..With respect to mountain passes, the main roads 
 alone will *reqn ire permanent works. It" the passes are inde- 
 pendent of each other, a work will be necessary for each one 
 separately; but where several unite at the same point, upon 
 or within the frontier, a single work, placed upon this point, 
 will suffice. Local circumstances will determine the point in 
 each pass which, occupied, will offer the greates^advantage of 
 obstructing the march of an invading force. The only rule 
 that can be given is that, whilst the position selected shall 
 satisfy this condition, there shall be every facility of communi- 
 cation between the fortress and the interior for receiving sup- 
 plies and reinforcements. This rule would lead generally to 
 the selection of some point of the outlet lying within the fron- 
 tier as the proper one. 
 
 647. ..The number of fine natural harbors and roadsteads on 
 our seaboard, where the largest fleets can find a secure an- 
 chorage at all seasons; the proximity to the ocean of many of 
 our most important cities, towns and populous villages, by 
 which they are not only exposed to the usual dangers of naval 
 attacks, but to incursions from an enemy's land forces; to- 
 gether w T ith the large rivers which, having their outlets on this 
 seaboard frontier, are navigable for long distances within it 
 by vessels of the greatest burthen, have given to the subject 
 of sea-coast defences a particular prominence among ourselves. 
 The means of defence disposable for the security of these 
 points, consist in permanent works arranged to meet an attack 
 both by sea and land, and of such strength as the presumed 
 nature of the attack will demand; of such temporary fortifica- 
 tions as the exigency of the moment may point out; of mova- 
 ble land forces; and of floating defences to act in aid of the 
 others. 
 
 648. ..The character of the permanent defences will depend 
 upon the object in view. Where this is simply to exclude an 
 enemy's fleet from the use of a harbor, or roadstead, which 
 
TO THE TOPOGRAPHICAL FEATUBEB OF FBONTBEfiS. 209 
 
 offers to him no other inducement for its occupation than that 
 afforded by a Becure anchorage, one or more small works of 
 sufficient strength to prevent the success of an open assault 
 upon them, armed witll heavy mortars and guns with long 
 ranges, that can reach by their fire every point where an 
 enemy's ship could safely anchor, will be sufficient. 
 
 649. ..The points to be occupied by these works, as well as 
 their plan, will depend upon the natural features of the har- 
 bor or roadstead. They will usually consist either of open 
 works, armed with guns in barbette and mortars that can 
 sweep all points of approach to and Within the harbor, or of a 
 combination of casemated and open works. The gorge of the 
 works in all eases being occupied by a casemated tower, of 
 sufficient Btrength and capacity to hold a garrison of sufficient 
 force to beat off an open assault on the battery by land, and 
 be itself secure from a coup cU main. Like defences will also 
 be sufficient for the security of the smaller classes of towns 
 and villages, which would probably oiler a temptation only to 
 a small naval force, 
 
 650. ..In the case of important commercial cities and large 
 naval depots lying within harbors more or less accessible both 
 to sea and land attacks, the character of the defences called 
 for should be commensurate with the magnitude of the inter- 
 ests to be guarded, and the consequent temptation to an enemy 
 to put forth great efforts for their occupation and destruction. 
 
 661...The avenues of approach to these objects by sea, which 
 can be brought within range of cannon and mortars, in forti- 
 fications on the shore, or in works erected on natural or 
 artificial island.-, should be occupied to a distance that will 
 prevent a fleel from approaching near enough to open a bom- 
 bardment ; and, it' practicable, should also force the enemy, if 
 he ventures a laud attack, to disembark his troop- cither al 
 
 • a distance from th<' object to lie reached that he will not 
 he aide, by a sudden d< et a surprise, or to limit 
 
 his lauding to such point tin their i 
 
 tion, may render tie the naval and land 
 
 27 
 
210 THE AHAPTATTOM OF 11 i:M.\.\iNT FOSTOTOATIOH 
 
 forces very uncertain, and, in case of a storm, place the latter 
 in a very perilous condition it" attacked. 
 
 652... i he exterior chain of the defences will consist of works 
 of the above character; Within these, batteries, either open 
 or casemated, as the locality may seem to demand, should 
 occupy all the most suitable positions both for sweeping tho 
 path that a fleet must' follow by powerful cross, direct and 
 enfilading fires, and for reaching every point of anchorage 
 within the harbor. On the land approaches, points should be 
 occupied by forts of a permanent character, which will pre- 
 vent a sufficiently near approach to bombard the city or depbt % 
 and, in combination with temporary works,afford an intrenched 
 field of battle for the troops on the defensive. These will 
 form the exterior line of the land defences ; the interior line 
 being either a continuous enceinte of permanent fortification 
 which will require a regular siege for its reduction, or else a 
 suitable combination of either continuous or detached iield- 
 Works of such strength and armament that the enemy, in any 
 attempt to carry them by an open assault, will be made to 
 suffer heavily, even if he is not repulsed. The security of ob- 
 jects of this character will be greatly increased when they lie 
 at some distance within the sea-coast frontier, and can only lie 
 approached either by water, through such comparatively nar- 
 row defiles as even our largest rivers present, or by land only 
 after one or more marches. These defiles will, for the most 
 part, not only present admirable positions on their banks from 
 which they can be enfiladed within the range of the heaviest 
 guns, but frecpiently others, at points where the river narrows, 
 oi- changes its course, where works, occupying the opposite 
 banks, will give the means of rendering the river impassable 
 by booms, rafts or other floating or sunken obstructions, which 
 cannot be removed except by getting possession of the de- 
 fences, by which they are guarded, by a land attack. 
 
 653... Wherever harbors or hays are of that extent that their 
 entrance cannot be interdicted to an enemy's fleet, nor secure 
 anchorage within them be prevented, of which we have ex- 
 
TO TIIE TOPOGRAPHICAL FEATURES OF FRONTIKKS. 211 
 
 ampleson our coast, the case falls beyond the province of for- 
 tification, and must be left to floating defences for a solution. 
 Sere even some fortified harbors on the shores of such exten- 
 sive estuaries may give secure places of refuge for ships of 
 Avar, from which they may at any moment sally when they 
 can take the enemy at disadvantage, or into which they can 
 retreat if attacked by a superior force. 
 
 654L..The necessity for fortifications for the security of fron- 
 tiers being admitted, there is seldom any doubt as to the points 
 to be occupied, as these are usually unmistakably marked out 
 by nature herself. Of the character of the defences for ti. 
 points, the features of the locality and the importance of the 
 points themselves to military operations, either defensive or 
 offensive, beyond the immediate range of their guns, must, 
 decide. Here the question comes exclusively within the do- 
 main of the engineer, and its solution will be more or less per- 
 fect as he has the ability to adapt, in the best manner, all the 
 urces of his art to the peculiar circumstances of the i 
 re him. 
 
 655...In the powerful military states of continental Europe, 
 the question, as to what extent the great centres of population 
 and wealth in the interior should be covered by fortifications, 
 has been submitted to the investigation of the ablest engineers 
 and statesmen, from the time of Vanban down to the pn - 
 day, but more particularly since the fall of Napoleon, a catas- 
 trophe which mighl not have taken place had Paris bee- 
 cured by fortifications, which would have prevented a con 
 main when the armies of the Allies gained possession of il 
 the resuli of a pitched battle. Whatever differences of opinion 
 have been called forth, as to the mode oi accomplishing this 
 object, as shown in the published views on the propositioi 
 fortify Paris, there seems to have been none, among tl 
 lied to decide upon it, as to the great important 
 fortifying this capital, and other large places in the hit 
 
 which, from their position, m the big 
 
 strategical value, in tin 
 
212 THE ADAPTATION OF PERMANENT I < >K'l II k ATIoN. 
 
 large army, as not only to prevent their wealth and resom 
 from falling into the possession of the invading force, but to 
 make them safe rallying-points for beaten and dispersed for 
 and depots for organizing new armies. The plan that has been 
 adopted for this end both in France and in most ut* the other 
 parts of Europe, w*hich have been either newly fortified or had 
 their old works strengthened within this period, is to surround 
 the city by a continuous enceinte of greater or less strength, 
 but one secure from a oowp dt main; and to occupy, with 
 forts of a permanent character, the most suitable points in ad- 
 vance of the enceinte, to prevent an enemy from bombarding 
 the city, or penetrating between the forts without first gaining 
 possession of them. By this plan, it is proposed to gain all 
 the advantages offered by the passive resistance of fortifica- 
 tions, and the activity of a disposable, movable force occupy- 
 ing the zone between the enceinte and the forts as an intrenched 
 camp, upon which the forts with temporary works thrown up 
 between them would render an open assault too perilous to 
 be attempted. 
 
 G5G...The enceinte of Paris consists of continuous bastioned 
 fronts without outworks, having a revetted scar}) of the usual 
 height to secure it from escalade, and a ditch with a counter- 
 scarp of earth. The advanced forts are either quadrangular 
 or pentagonal bastioned works, enclosing all the means of se- 
 curity for their garrisons, as bomb-proofs, etc., their plan being 
 skilfully adapted to the site, and to their mutual bearing on 
 the defence. The fortifications of Lyons present more diver- 
 sity, both in the plan and details of the enceinte and forts, 
 although the general system is the same as that of Paris. In 
 the last is seen a more extensive application of casemated ami 
 gallery defences, both for exterior flanking and for the defence 
 of the interior of the forts; growing out of the more broken 
 features of the site generally, and frequently from the more 
 coniined space occupied by them. 
 
 (557. ..In Germany, the same general system of a continuous 
 enceinte, with strong advanced isolated works, has been fol- 
 
SUMMAKY OF THE PROGEE88 OF FORTIFICATION. 213 
 
 lowed, the whole being planned and combined according to 
 the distinctive features of what is known as the German system 
 of fortification. 
 
 658.. .In our own country, where our largest centret of popu- 
 lation and wealth lie almost immediately upon the seaboard, 
 it would seem impracticable, in view of the rapid spread of 
 population around them, and the consequent changes in local 
 features, to resort to any defences of a permanent character, to 
 secure them from a land attack, even were the nation willing 
 to assume the burthen of the great outlay for such an object, 
 as in a few years the works %f to-day might be rendered uso- 
 lesa by the changes referred to. Even in Europe, the strongest 
 despotic governments have been obliged to cede, what seemed 
 military exigencies, to the demands of the social condition, 
 and either to raze the fortifications of cities, to give room to a 
 crowded population, or else t<» suffer such encroachments on 
 the ground necessary for the functions of the works as to 
 rentier thorn nearly useless. The only defensive resource that 
 seems left to ourselves, in like cases, is in the use of field 
 works, one which our military experience shows may he relied 
 UpOll with confidence, BO long as the military aptitude of OUT 
 population remains unchanged, from what it has thus far been. 
 
 SIMMY OF THE PROGRESS OF FORTIFICATION 
 
 9.. .The records of history and the vestiges of remote civili- 
 zation show that the art of fortification, in some ; an- 
 other, has been in practice throughout all nations, < ven in the 
 lowi u, and that, wherever it has i 
 cultvated, i; ter has been mo - influenced, no< 
 
214 sl'MMAKY 01 THE PROGRESS OF l OB 1 11- 'Ii ATION. 
 
 only by the natural features of the country, bul by the politi- 
 cal and social conditions of its inhabitants. In its earliest ap- 
 plications, we find men resorting to one or mure simple enclo- 
 sures ol earthen walls; or of these surmounted bj 
 placed in juxtaposition; <>r of stakes alone firmly planted in 
 the ground with a strong wattling between them; or of timber 
 in its natural state, having it.- branches and the undergrowth 
 strongly interlaced to form an impervious obstruction, with 
 tortuous paths through it, known only to the defenders. 
 
 660...A resort to such feeble means shows not only a very 
 low Btate of this branch of the military art, but also of that of 
 the attack, as defences of this kind would present hut a slight 
 obstacle, except against an enemy whose habitual modi' of 
 warfare was as cavalry, or of one not yet conversant with the 
 ordinary plans for pealing. This class of fortifications for the 
 defence of entire frontiers has been mostly met with in the 
 east of Europe, and was, doubtless, at the time, found to b 
 sufficient protection against those nomadic tribes that for : 
 have roamed over its vast plains, and who are only formidable 
 as a mounted force. 
 
 'Hil. ..The next obvious, and, in humid countries, necessary 
 step was to form -walls either of rough blocks of stone alone, 
 or of these interlaced with the trunks of heavy trees. Ob- 
 structions of this kind could only be used to a limited extent, 
 and were confined to the defences of places forming the early 
 centres of population. As human invention was developed, 
 these, in their turn, were found to present no serious obstacle 
 to an assault by escalade — giving to the assailed only the tem- 
 porary advantage of a more commanding position — and they 
 gave place to walls of dressed stone, or brick, whose height 
 and perpendicular face alike bade defiance to individual at- 
 tempts to climb them, or the combined efforts of an escalade. 
 From the tops of these inaccessible heights, sheltered in front 
 by a parapet of stone, and, in some cases, by a covered corri- 
 dor behind it, the assailed could readily keep at bay any 
 enemy, so long as he could be attained by their missiles; but 
 
SUMMARY OF THE PROGRESS OF FORI II l< I \TION. 215 
 
 having* reached the foot of tine wall, he here found Bhelter 
 -from these, and, by procuring any cover that would protect 
 him from objects thrown from above, could securely work at 
 effecting a breach by mining. It was probably to remedy this 
 defect of simple walls that towers, which, at first, were nothing 
 more tlian square or semi-circular projections built, from dis- 
 tance to distance, in the wall itself, were first devised. These, 
 subsequently, were not only enclosed throughout, but divided 
 into stories, each of which was provided with loop-hol< 
 flank the adjacent towers and the straight portions of the wall 
 between them, and was isolated at top from the straight por- 
 tion of the walls adjacent to it by a break or ditch, on the 
 interior, between the towef and the wall, across which a com- 
 munication between the two could be established by a tem- 
 porary bridj 
 
 , oT>2.. .These formidable defences were, in their turn, found to 
 be insufficient against the ingenuity and skill of the assailant, 
 who, by means of covered galleries of timber, sometimes above 
 iii*l and sometimes below, gradually won his way to the 
 foot of the wall, where, by breaking his way through it, or by 
 undermining and supporting it on timber props, to be subse- 
 quently destroyed by fire, he removed the sole obstruction to 
 a bodily collision with the assailed. In addition to these means 
 the Ik- some cases, resorted to tl lofty wooden 
 
 towers, which were covered by raw hides to protect them from 
 tire, from within which an in shower of arrows and other 
 
 missiles was directed against the assailed. These ponderous 
 engines were gradually moved toward the walls, on inclined 
 phu i with incredible toil, to give th 
 
 Bailants a commanding position, and to enable them, when the 
 tower was brought sufficiently near to the wall, to he, 
 drawbridge from it. to bridge the chasm, and bring on a hand- 
 to-hand contest with tin' assailed. 
 
 methods of attack led to new modificatio 
 the def nee, which « urrounding the place by wide 
 
 of which the walls formed theacarp — the 
 
216 M M.MAKY OF THE PEOGEK86 OF FOBTTFICATIOH. 
 
 counterscarp being either of earth 6r revetted with stone, 
 placed a formidable obstacle to the mode of attack by 
 mining, as well as to the ase of earthen mounds, as these Last 
 had i" be erected across the ditch before sufficicient proximity 
 tn the wall could lie gained, either to form a communication 
 with its top, or to plant the battering ram — a heavy beam, 
 with an iron or brass bead, which, swung horizontally within 
 a wooden tower, could he driven by men with sufficient fo 
 to breach the heaviest walls. The ditches, also, were tilled 
 with water whenever this obstruction could he procured. 
 When dry, they formed a defile through which the assailed 
 often sallied upon the assailant with Buceess. 
 
 664.. .The gigantic proportions often given to the fortifica- 
 tions of antiquity, as well as their extent, seem almost iucredi- 
 ble in the present day. In many cases a double wall of Btone 
 or brick was rilled in between with earth, forming a wide rang 
 pail upon which several vehicles could go ahreast. !Not only 
 was the space enclosed within the walla sufficient for the habi- 
 tations, but ground enough was -aid to he taken in. also, for 
 agriculture, so as to add considerably to the food of the in- 
 habitants and cattle, for the long periods to which hlockades 
 
 were in many cases extended, when the besiegers had failed 
 in all other means of reducing the place. 
 
 6651. .The wall built by the Romans in Britain, between Car* 
 lisle and Newcastle, to restrain the inclusions of the Pictfl into 
 the southern portions of the island, was sixteen miles in ex- 
 tent, about twelve feet in height, and nine feet in thickn 
 The extent and dimensions of this work sink almost into 
 insignificance when compared with those of the celebrated 
 wall of China, built to restrain the incursions of the Tartars. 
 This structure is about 1,500 English miles in length, has a 
 height of 27 feet, it.-, thickness at top being 11 feet. The lower 
 portion of it is built of dressed stone, the upper of well hurned 
 brick. It is flanked at distances of about 80 yards apart by 
 towers, in which iron cannon are found. In the' great extent 
 it embraces, it necessarily crosses hills and valleys, and in 
 
SI'MMAKY OF TIIK PROGRESS OF FORTIFICATION. '2 1 7 
 
 many places important defiles. An examination of its parts 
 has shown that in its plan there was an evident design to 
 adapt it to those features of its site, as it is well thrown hack 
 to the rear <>t' difficult passes ; and, at points where there is 
 most danger to be apprehended from invasion, there are sev- 
 eral walls in succession. 
 
 666../The mode of attack of fortified places resorted to by 
 the ancient.-, was reduced to settled rules and brought to the 
 highest state of perfection by the Greeks, about the epoch of 
 xander the Great, and the immediate successors to his vast 
 conquests. An essential feature in it, whether in the Bieg< a of 
 inland fortresses or of those on the seaboard, was to cutoff all 
 communication between the place and the exterior, by hem- 
 ming it in bysea and land ; with stationary forces, covered them- 
 selves, by lines of intrenchments strengthened by towers, and, 
 iii tl isl place,-, also by fleets. The 1 
 
 were thus prepared to repel all assaults, both from without and 
 
 from the invested place. Having selected the portions of the 
 
 place on which the main attack was to be directed, a second 
 line was formed parallel to the first, which was covered, and 
 constructed of timber and wicker work, and secured with raw 
 hide- to prevent its being set on fire. From this sheltered po- 
 sition, which Berved also the purposes of a lodging for the be- 
 i rs, the were annoyed with missiles thrown from 
 
 all the artillery known in that day. consisting of the ordinary 
 bow. the cross-bow, and the varioii- machines for projecting 
 
 heavy stones and other projectiles. Under the diversion thus 
 made, the 1" pushed forward from this line several COY' 
 
 ered approaches directly upon the place, for the put 
 gaining the count* recarp, and from that position filling tip the 
 ditch with Btones, earth, heavy bags, etc., bo prepare the way 
 for placing the battering-ram in position to breach the wall. 
 The tower in which this machine wn> placed usually e 
 
 by troops, who cleared 
 the top of the wall of the b 
 
 quently aided b high towers, which ced 
 
 28 . 
 
218 MMMAin 01 THE FBOGR1 RTIFICAT10H, 
 
 either on the natural level of the ground, or upon artificial 
 mounds, forming inclined planes, bo that any desirable com- 
 mand over the interior could be obtained* 
 
 667...The defence was mostly of a passive character: the 
 besieged trusting maialy to the strength of their defer 
 kinder cover of which'they resorted to all the means used by 
 the Besiegers, for attaining the latter when they came within 
 reach o\ their missiles ; nsing, tor the near defence, cranes and 
 other devices to seize upon the implements planted at the foot 
 of the wall ; and constructing galleries of countermines to 
 overwhelm the artificial monnda and their towers, 
 
 668... The Romans evinced their decided military aptitude, 
 not only in the employment of the ordinary systematic meth- 
 ods of the attack and defence of fortified places, but in their 
 application of the cardinal principle of mutual defensive rela- 
 tions between the parts of a fortified position, obtained by 
 advanced and retired portions of the enceinte; and also in 
 the adaptation of intrenchments to the natural features of the 
 site, as shown in the fortifications of some of the permanent 
 frontier camps of their military colonies. The application of 
 these principles ha\ e also been noticed in some of the fortified 
 positions of India, which consisl of a mural enceinte with 
 earthen ramparts, Hanked by round tower.-, and of round tow- 
 er.- in advance of the enceinte and connected with it by capon- 
 nieres. 
 
 669... With the decadence of the Roman empire, the art of 
 
 fortification, like the other branches of the military art, was 
 brought to so low a stage that Btrongholds which, defended 
 
 with skill and energy, would have baffled the eil'orts of a well- 
 trained assailanl in the art of attack, fell, almost without re- 
 sistance, into the possession of the fierce Northern hordes by 
 which the whole of civilized Europe was overrun. The re- 
 mains of the structures raised for defensive purpose.-, during 
 the prosperous days of the empire, were probably the sole 
 means of protection afforded to the inhabitants of the towns that 
 still maintained a nucleus of population, until the rise of the 
 
 
 H 
 
SUMMARY OF THE PROGRESS OF FORTIFICATION". 219 
 
 Western empire under Charlemagne; and it was the necessity 
 fell by this conqueror, not only of securing his conquests, btit 
 of checking the irruptions of the barbarous tribes along his 
 extended frontier, which Led him to erect t&tes <l< pant on the 
 frontier rivers, and a line of strong to.wers, for garriaona of a 
 few men, upon the most inaccessible ami prominent points of 
 this frontier; the latter being a means which was subsequently 
 r a like purpose in the Spanish peninsula. Henry 
 I., bf Germany, introduced a more important and more syste- 
 matic a<l<liti<>n to these permanenl frontier defences, by sur- 
 rounding the frontier towns and villages, occupied by military 
 Colonists, with walls and ditches, to secure them from such at- 
 tacks us they might be exposed to. and. subsequently, by add- 
 ing a second line of strongholds within the frontier, by which 
 an irruption 1 through the frontier line mi^ht still he checked. 
 07O...During the general disorganization of states under the 
 feudal system, the {\-r<- cities, which depended for their de- 
 fence .,n the burghers composing the different crafts, every 
 individual who could maintain a t'ew retainers in his pay, ami 
 the clergy even resorted to such means of defence as would 
 re them from the attacks of Others in a like condition, 
 or- which would enable them to carry out that s} r stem of pill a 
 that had beco eral amongst the nobles and other military 
 
 chief tail 
 
 !...l'"roin this state of society wrung Up tie 
 
 placed in the most inaccessible positiooa on the lines of com- 
 munication which the little inland commerce that was still 
 carried on was obliged to tra I 
 
 vided with every possible device for an obstinate passive de- 
 ing surrounded by a wide and deep ditch, or moat, 
 
 •which a drau-ln the only communication t.< the 
 
 main entrance, which, il on the 
 
 rior and closed w ith n doors; the tortuo 
 
 which led from tie I 
 furtk 
 at a moi the 
 
MMMAHV OF mi. PKOGBE8E OF FOB 1 OTI0ATTON. 
 
 ordinary measures of loop-holes and machicoulis in the walls 
 and tower.- for annoying tin' assailant, a high interior tower, 
 termed a keep, or donjon, was often added, which, command- 
 ing the exterior defences, served also as a watch-tower over 
 the adjacent country. 
 
 672. ..'Hie keep, being the last defensible point, was in some 
 cases provided with a secret subterranean passage, having its 
 putlet in a distant concealed spot, through which .succor could 
 be introduced into the beleaguered castle, and, in the last ex- 
 tremity, the garrison find safety in a stealthy flight. 
 
 673. ..The fortifications of towns partook of the same charac- 
 teristics as those of castles. From the custom of assigning to 
 the different burgher crafts, each of which had an independent 
 military organization, the exclusive guardianship of portions oij 
 the enceinte, as well as their erection and repairs, great diver- 
 sity, and, frequently, a whimsicality, in the defensive arrange- 
 ments, was the natural result; the evidence of which still ex- 
 ists in the remains of the walls of some of the old continental 
 cities. The art, for the most part, was practiced by ambula- 
 tory engineers, who, like the secret orders by whom the bridges 
 and churches of the same period were built, ottered their ser- 
 vices wherever they were wanted. Many new ideas were also 
 introduced from the East by the Crusaders, as exhibited in the 
 fortifications of castles and cities belonging to the templars 
 and other religious military orders. 
 
 674.. .With the invention of gunpowder and its application 
 to military purposes, a gradual revolution took place in the 
 general forms and details of fortification. It was soon seen 
 that naked walls alone did not afford space enough for the new- 
 military machines, nor sufficient protection against the projec- 
 tiles thrown from them. This led to the introduction of earthen 
 ramparts and parapets, which were placed against the walls 
 and suitably arranged to meet the exigencies arising from this 
 change. The art began to receive something like a scientific 
 basis about this time in Italy, from which the names and forms 
 of most of thi' elements of fortification now in use are derived. 
 
SUMMARY OF THE PROGRESS OF l'< >K'i !!■ T« \TION. 221 
 
 The Italian engineers, like their predecessors, went from state 
 to state t<» offer their services wherever they were needed, and, 
 in tli is way, disseminated the principles of their scl 1 through- 
 out Europe. It was at. this epoch that the bastioned form of 
 fortification first appeared, hut the precise date and the author 
 of the invention are both unknown. With its introduction, 
 the importance of separating the parts of a line of fortification 
 into advanced and retired parts % the hitter flanking and defend- 
 ing the former, seems to have been recognized as an essential 
 principle of the art. With these changes in the form of the 
 enceinte the art was gradually improved, by the addition of 
 outworks to increase the amount of cross and flank fire ; the 
 introduction of bomb-proof shelters for the troops and other 
 purposes; the substitution of earthen for stone parapets; and 
 the attempt to conceal the scarp walls from the enemy's bat- 
 teries, by decreasing the command and deepening the ditches 
 
 of the enceinte. 
 
 675...By these gradual changes, stone walls, which in the 
 old fortifications were the essential defensive feature-, came 
 at length to l.e regarded in their true character, Bi'mply as pas- 
 sive obstacles to an open assault by escalade. The property 
 of earthen parapets of resisting, without material loss of 
 strength, the long continued fire of the assailant's lea- 
 guns, showed that the same defensive means were applicable 
 both to works of a permanent and of a temporary character, 
 and were equally available for the purposes of the assailant 
 and the assailed. The measures for the attack and for- the de- 
 fence of positions were thus reduced to the sa general prin- 
 ciples, differing only in the forms and dimensions of the ■ 
 mentary parts, ;i- circumstam led to demand. 
 
 676...Italia2* School. A> above stated, the first employ- 
 ment of hasl ist, was made by the Italian 
 far ;i- ha ined, toward the 
 the fifteenth, or the commencement of tl enth 
 tury. To whom the credit of their invention is due, 
 not known. In the earlier fronts of the ]• bool the I 
 
222 SUMMARY OF THE PROGRESS OF FORTIFTOATION. 
 
 tions ire very small, and they are connected by curtains vary- 
 ing frotn 250 to 500 yards in length. The bastion flanks, 
 which were usually perpendicular to the curtains, were divided 
 into two portions ; that aext to the curtain, which was one- 
 third of the entire Hank, was thrown back, and covered by the 
 portion in advance; the advanced portion, thus formed, re- 
 ceived the name of the orillon. The lower part of the retired 
 portion was casehiated for cannon ; and behind this, and sepa- 
 rated from it by a dry ditch, ruse a second think, having the 
 same command as the other parts of tin- enceinte parapet. 
 In .-.mie cases, a small and very obtuse bastion was erected at 
 the middle of long curtains. The ditches of the enceinte 
 were usually about 100 feet wide, and l'4 feet deep, the coun- 
 terscarps being parallel to the bastion faces. A scarp gallery, 
 for the purpose of mining, ran throughout the enceinte scarp, 
 and communicated with galleries leading to other points. The 
 parapets, at first of masonry, were afterward of earth, and 
 made from IS to 2-i feet thick. The earth of the rampart was 
 sustained on the interior by a wall. Ramps established a 
 Communication between the interior and the rampart. 
 
 677.. .The defects of these early fronts were soon felt, and 
 a more complicated hut improved trace adopted, in which the 
 bastions were enlarged, and the curtains diminished. The re- 
 tired thinks were still retained, but the orillon, instead of being 
 angular, was rounded. To these improvements cavaliers were 
 sometimes added to the bastions, which, in those cases, were 
 made without retired thinks, or they were placed on the cur- 
 tains, when, from the configuration of the site, some portion 
 of the ground within cannon range could not he swept from 
 the enceinte; parapet. The covered-way was introduced, and 
 became an integral part of the front; and a small demilune 
 or ravelin was placed in advance of the enceinte ditch, form- 
 ing a tete de pont to cover the communication, at the middle 
 of the curtain across the main ditch, between the enceinte and 
 the exterior. The covered-way, which at first was of uniform 
 width, and bordered the main and demilune ditches, was snh- 
 
8UMMAKY OF THE PBOGEE88 01 FOBTIFIOATKHSF. 228 
 
 sequently provided with salient and reentering places of arms. 
 These various essential parts of a fortified froni were gradually 
 ameliorated by the Italian engineers, bu! not before the Ita- 
 lian school had left its impress upon the fortification of all the 
 Other states of Europe, as the Italian engineers, from their su- 
 perior acquirement.-, were in demand throughout these, states. 
 
 678.. .Spanish School. This school, as seen in the existing 
 fortifications of Spain, shows the influence of the Italian 
 school, though modified by national characteristics. These 
 are observed in the greater dimensions given to their profiles, 
 an augmentation of the. means of annoying the besiegers by 
 artillery and musketry, the construction of complex interior 
 retrenchments, and, frequently, the omission of a coven-d-wav : 
 the entire organization of the works pointing toward an ob- 
 stinate passive defence, rather than to one in which sorties 
 may play an essential part — a mode of defence in which the 
 Spaniards, at all periods of their history, have exhibited con- 
 summate skill and perseverance. 
 
 From the broken character of many of the sites of their for- 
 tifications, the Spanish engineers have resorted to detached 
 Works to occupy commanding positions in advance of the main 
 work. These detached works are also organized for a purely 
 passive defence; being left to their own resources rather than 
 iy BUpport from the main work. 
 
 < *► 7 1 ♦ . . . I > • i < u School. This Bchool took its rise in the politi- 
 cal qec< of the tinn.-. in which the national spirit was 
 aroused to throw off an onerous foreign yoke The aquatic 
 character of Holland, and the want of time 'and pecuniary 
 meat lients of defence which are n< 
 wanting under like circumstances. Tie deficiency of eartlj 
 led to the formation of low parapets for the main enceinte, ami 
 wide ditches filled with water. The main enceinte was usually 
 
 '■oiid one with a very low parapet, t 
 the surfacM of the wet ditch; and this Becond enceinte 
 
 arated from the fii dry ditch, which favored Borl 
 
 and which v. ded with all the I - palisad* . 
 
L'L'l si MMAKV OF THE PBOORE8S OF FORTIFICATION. 
 
 hours and block-houses, for offensive returns and surpri 
 The second enceinte was covered by a glacis in advance of the 
 main ditch. The covered-way left between the glacis and the 
 ditches was, to a great extent, frequently deprived of its 
 
 ial offensive feature, by the introduction of an exterior 
 wel ditch, placed at the foot of the glacis and enclosing it j 
 over winch communication with the exterior was kept open by 
 temporary bridges. The work.- were usually greatly multi- 
 plied and their combination complicated. The whole of the 
 defensive measures of this school seem to have had for their 
 object a strictly passive resistance. With this view, long ii 
 of entrenchments, supported, from distance to distance, by 
 tort.-, connected their frontier towns and villages, affording 
 Miilicient obstacle to marauding expeditions, by requiring the 
 efforts of a strong force to break through them. At a later 
 period, taught by the experience of their earlier efforts against 
 the most military state of that epoch, covers thai would afford 
 
 iirity against incendiary modes of attack were provided; 
 and reveteraents of masonry substituted for the earthen slopes 
 of the ramparts, particularly where the ditches were dry. 
 These successive changes, partly induced by the Italian and 
 Spanish schools, with whose methods the hutch engineers he- 
 came acquainted through their connection with Spain, were 
 the natural precursors of the methods of Coehorn, the most 
 distinguished engineer ot the Dutch school, whose works are 
 characterized by many of its essential features. 
 
 680... < ii-:i:.M an School. The Germans reckon a number of 
 original writers on fortification, among the most noted of whom 
 are the celebrated painter Albert Durer, Daniel Speckles, and 
 Kimpler. In the propositions of these writers are to be found 
 the influence which the Italian school naturally exercised 
 throughout civilized Europe, and the germs of many of the 
 view.- held by the German school of the present day, which 
 last seem, however, to have been taken more immediately 
 from the propositions of Montalembert and Carnot. 
 
 681. ..Swedish School. The part played by Sweden upon 
 
summary OF Tin: PROGRESS Of FORTIFICATION. 225 
 
 the theatre of Europe, under her two celebrated monarchs, 
 
 Gustavus Adolphus and Charles X II.. served to de\ el,.], in this 
 nation every branch of the military art. A number of dis- 
 tinguished generals and engineers arose under these monarchs, 
 who combined, with the practice of their profession, a study 
 of its theory. Among the engineers of this school Virgin 
 holds the first place. The climate and the nautical habits of 
 a large portion of the Inhabitants seem to have led to the con- 
 struction of land defences analogous to those of ships; as 
 shown in the use of casemated batteries in several tiers, both 
 for sea-coasi and inland fortifications. In this school the bas- 
 tioned system seems to have been generally adopted for the 
 enceinte, great attention being paid to covering the faces of 
 the works from enfilading fire, to providing casemates having 
 reverse views on the besieger's works, and particularly in so 
 arranging the interior defences that each part should not only 
 contribute to the support of the others, but be capable of an 
 independent resistance. These dispositions necessarily led to 
 at complication and multiplicity of works, as shown in 
 the writings of Virgin. 
 682...Fbbn< u School! What may be termed the character' 
 this seho.,1 are to be seen rather in the method of 
 Cormontaingne, and the teachings of the two celebrated 
 
 Schools, Mi zieres arid "Met/, for the education of eiiL.Mii' 
 than in the practice of Yauhan. although his authority ha- 
 
 <d a preponderating influence throughout Europe; and is 
 still appealed to. in all great problems of the art, by i i 
 in polemical disput< s. Tic In neb have evinced in tl 
 all the other arts, that spirit of systematic combination wl 
 form ' their most striking national trait-. \\ I 
 
 eluding an active defence, the most noted authors of I 
 
 •ased their methods more upon R ootnbinatiou of 
 elements by which the can he c 
 
 by stop, by the lire of | - than h Until 
 
 within the last thirty or fort; 
 
 peri . and 
 
 28 
 
226 PROGRESS "I THE ATTACK 
 
 a subjection t<> mere authority. This accusation, hdwever, 
 true rather of the polemical writings of the day, growing out 
 of the propositions of Montalemb< rt, than of the practice of 
 the French engineers; and it was, iu a measure, strengthened 
 by a miscohception on the part of foreign engineers, of the 
 real purposes of the instruction given in their schools of pro- 
 nonal training. Still, recognizing in Yanhan and Cormon- 
 taingne tin- chief founders and authorities of their school, the 
 French engineers of the presenl day discard no defensive ele- 
 ment that has stood the test of experience, or is consonant 
 with Bound professional views. Basing their art npon incon- 
 brovertable principles, its practice is made by them t<. conform 
 to the exigencies of each case a-- presented by it> own data. 
 
 PROGRESS OF THE ATTACK SIXCE THE 
 INVENTION OF FIREARMS. 
 
 683.. .Tin' introduction of cannon, although it led to important 
 changes in the measures bojh of the Attack and defence, still 
 did not, for a considerable period, bring about any very decie 
 results in the length of sieges. The means which it afforded 
 the defence of reaching the * besiegers at a distance, and de- 
 stroying all the methods of approaching and annoying the 
 place which had been hitherto used, led to the substitution of 
 the ordinary trenches of the presenl day lor the wooden gal- 
 leries and other similar expedients tor approaching under 
 cover ; and to the erection of batteries at distant points to open 
 1. reaches in the walls. Lines of circuinvallation and counter- 
 vallation, which formed so prominent a feature previously to 
 this epoch, was the only one which still kept its place, as it 
 
 
SINCE ill i ; iwiaiio.n <U' nKRARMB. 2'_'7 
 
 has done to a greater or Less extent to the present day. For 
 the purpose of effecting at) entrance into the place, breaching 
 batteries were erected opposite the points deemed most favora- 
 ble. They were placed either on natural elevations <>f the 
 ground or upon artificial mounds, with the object of attaining 
 the wall to be opened near its foot and thus form a breach <>f 
 easy ascent. These batteries were enclosed in works of suffi- 
 cient size and strength to hold garrisons to secure them from 
 sorties. The approaches were made as at present 1>\ zig-2 
 along the capitals of the salients, to the counterscarp, where 
 a covered descent was made into the ditch, opposite the breach, 
 preparatory to its assault. When the wall was not exposed to 
 a distant fire, the besiegers were" obliged to carry the covered- 
 way by assault and establish their breaching batteries on the 
 at of the £ In carrying forward these works, the he- 
 
 were subjected to great losses and delays, owing to the, 
 magnitude and multiplicity of the works they were obliged to 
 complete : to the imperfect character of their artillery and the 
 faulty position of their batteries, by which they were unable 
 (0 keep under the fire of the place; the want of connection 
 between the separate approaches; and the exposure <>t' the 
 wi nk men in the trenches to sorties, the troops for their support 
 
 in the enclosed works in the rear being t listant to . 
 
 timely succor ; besid enclosed works naturally 
 
 became the chi< f objecfta for the lire <>t' the besieged, the 
 glomeration of troops in them added materially to the 1- 
 Owing to these imperfections in then 
 
 sure.- of attack, the lie to make a 
 
 and prolonged d< :• became the m<.>t in 
 
 military operations of this period, in which captains of the 
 brity sought for opportunities of distinctio 
 - I...i!ut littli made in the D just 
 
 ribed, until Yauhan appeared upon the - 
 :-lv to him, Montluc, a distinguished French and 
 
 ad introduced short brai 
 which were run out from tin 
 
228 pro mi aii \< k 
 
 few troops for the immediate protection of the workmen, but 
 these were found to be very insufficient in repelling sorties of 
 any strength. The event which seems to have had the great- 
 on the subsequent progress of both the attack 
 and defence was the memorable siege of Candia, in which 
 volunteers from all parts of Europe were engaged, who, after 
 its close, disseminated throughout their respective count] 
 the results of the exp< rience they had there acquired. 
 Whether the idea of the parallels, now in use in the attack, 
 originated there, <<r with Vauban, this eminent man was the 
 first i<> establish them in a systematic manner, and to demon- 
 strate 1>\ experience their controlling importance in repressing 
 sorties. The introduction of this important element in the 
 attack; the concentration of the fire of batteries, by giving 
 them enfilading positions; the invention of the ricochet, as the 
 most powerful destructive means against the defences; the 
 avoidance oi open assaults, which, even when successful, arc 
 made at a great sacrifice of life, preferring to them the Leu 
 brilliant but slower method of skill and industry, by which 
 the Mood of the soldier is Bpared, and the end more surely 
 attained, such are the important service- which the attack 
 owes to Vauban; which has given it its present marked 
 superiority over the means of defence; and to which the 
 oce and experience of engineers since his day have added 
 nothing of marked importance. 
 
 685... Com ii H'>.\. Whil.-t the attack has thus been brought 
 to such a Btate of perfection, and its destructive means arc 
 still on the increase, from the rapid improvement daily making 
 in the range and certainty of aim of cannon, as well as in the 
 ease with which the mosl gigantic armaments can be now 
 transported to distanl points, both on sea and land, the means 
 of deft nee. bo far as relates i" fortification alone, are hut little, if 
 at all, in advance of what they were in the time of Yauham 
 Upon the chief defects and wants of the art, there exi.-ts hut 
 slighl divergence of opinion among engineers generally; not 
 so with respect to the remedy; opposite opinions being fre- 
 
SINCE THE QJVENTIOH OF IIEEARM8. 229 
 
 quently drawn from the same class of facts, and the same 
 authority frequently cited to sustain opposite, views. Whilst 
 eacli new dispntant denounces systematizing and rl 1 ■ ■ systems 
 
 of Others, his remedy for tlie abuse complained of is n.-ually :i 
 Bystem of his own, which not unfrequently oners but the 
 disjecta ?nembra of those of others. The Bum of the whole 
 matter is, that fortification is an art the component elements 
 and principles of which are tew and simple. It.- efficiency 
 Consists neither in short lines of defence nor long lines of de- 
 fence; nor in large or small bastions; nor in the adoption of 
 this or that system; but in the judicious adaptation of these 
 principles and element.- to the locality to he defended, and 
 
 the purposes of the defence. Til this resided the excellence of 
 
 the engineer's art. lie who should combine his element?- in 
 the arrangement of a small work, with a Weak garrison, as in 
 one intended for the occupation of an extensive position by a 
 large force, or should blindly adopt the same method.-, for an 
 iiregnlar site that he would for a horizontal one, whatever his 
 acquisitions or pretensions may lie, has but a small claim on 
 the title of military engineer. 
 
 686~.From the preceding brief summary, it will he seen 
 that the art of fortification, in it- progress, has kept pace with 
 the measures of the attack ; •• bavingh 
 
 brought about by changes either in the arms used by the 
 lant, or by the introduction of some new mode of assault. 
 The same cauw - isl continue to produce the same eflR 
 At no past period has mechanical invention, in it- bearing on 
 the military art. been m< re than at the present day. 
 
 The improvement that ; made in the r.r 
 
 and accuracy of aim of both small arms and cannon, the par- 
 tial adoption of wrou^ht-iron and steel for floating : 
 and men! of 
 
 important epoch in the irt. Tie 
 
 cannon will the aasa 
 
 in the selection of pxj iud will thus in- 
 
 crease the diflicultiee in adapl s to 
 
230 PROGRESS OF THE ATTACK. 
 
 the site, and in giving adequate Bhelter to the garrison and 
 armament. Whilst the defence will be to this extent weak- 
 ened, the approaches of the r will be rendered more 
 
 ]m rile us and more difficult, from the greater range and accu- 
 racy of small arms. The greal destruction of life, in open 
 alts, by columns exposed within so long a range, must 
 an additional value to intrenched fields of battle; and we 
 may again see fieldworks play the part they did in the defence 
 of Sebastopol; and positions so chosen and fortified that not 
 only will the assailant be forced to intrench himself to assail 
 them, but will find the varying phases of his attack met by 
 corresponding changes in the defensive dispositions. 
 
 687. ..The engineers of our own country, without servilely 
 copying any of the Bystemi in vogue in Europe, have, in most 
 of their enclosed works of any Bize, adopted the bastioned sys- 
 tem. As the works erected by them are chiefly for sea-coast 
 defence, their water fronts usually consist of one or more tiers 
 of casemates surmounted by a barbette battery; whilst the 
 land fronts present a rampart arranged for open defences. In 
 small works, where the properties of the bastioned Bystem 
 could not be developed, owing to the limited Bize of the fronts, 
 flanking dispositions have been made, either by casemated 
 capohnieres or by counterscarp galleries; and. in cases wh 
 a Large amount of fire was requisite to sweep a given ap- 
 proach by sea, they have resorted to the castellated form oi 
 
 casemated batteries; combining several tiers of casemates 
 
 with a barbette battery on tdp. 
 
 Whilst thus adhering to well settled principles and the prac- 
 tice of the besi European authorities, our engineers have con- 
 tributed their share to the improvement of the details of the 
 art. The works erected by them, within the last thirty or 
 forty year.-, are remarkable for the excellence of the materials 
 employed l»y them, the superior skill shown in the workman- 
 ship, and the care with which every detail is worked out to 
 subserve the object in view. In these respects and in the 
 general adaptation of the plan to the site, it is not claiming 
 
IXFi.i I v I OF li:i:i <•! I ,.\i;i m- OF BITE. 231 
 
 too much to Bay that the works erected by them are Dpi Bur- 
 passed, and, in sonic points, Dot equalled by any similar 
 works in Europe. 
 
 RIFIMCE OF IRREGULARITIES OF SITE (IX THE FORMS 
 
 AMI G0HM1HH OF THE ELEHEMS OF 
 
 PER1AXE.VT WORKS. 
 
 ■i treating the subject of permanent fortification, the 
 same order is nsnally followed as in the discussion of tempo- 
 rary fortification, viz: 1st. An exposition of the general prin- 
 ciples with their applications to a horizontal site. 2d. ' 
 various modifications of detail occasioned by irregularities 
 ttted in nature. 3d. The various accessory m< 
 itrengthening weak points, called for by peculiar circum- 
 of locality, which either preclude the applicatioi 
 the ordinary means or require others in addition to them. 
 
 39...Whether the - rfecdy level within the range of 
 
 the fire of the work «»r i- irregular, tin d condil 
 
 arr to 1"' satisfied in each case, in order tliat tin- work shall 
 have all the efficiency of which it is capable. These are: 
 Thai or to the <;■ r which 
 
 enemy must approach them, or from which he can am 
 them by his fire, i be brought ander the fire of 
 
 2cl, That ii" point of left 
 
 uanled l»y their own fin , 
 the • porary shelter from fin . ma 
 
 tinn 
 
232 i.mi.uvi "!' i i:ki:< .ti.a i:t 1 1 i:s of site. 
 
 within the defences shall be sheltered from the enemy's fire 
 in any position he may take exterior to them. 
 
 690...The problem presented for solution to the engineer in 
 irregular sites is, frequently, one of no ordinary complexity ; 
 demanding a minute and laborious Btudy of the natural fea- 
 tures of the position in their relations to the defence; c>n- 
 Dected with a tentative process, of which the object is so t<> 
 modrry the plan, relief ami details ordinarily adopted, as to 
 adapt them in the best manner to the given position. X<» 
 rules, hut of a very general character, can he laid down for 
 the guidance of the engineer in such cases. Of this class the 
 following are the most obvious and essential, and, when prac- 
 ticable, should he adhered to : 
 
 691. ..1st. It has already been observed that, from the means 
 used in the attack of permanent works, the more plunging the 
 fire of the work the more efficacious will it prove in retarding 
 the enemy's progress. The efficiency of this fire will depend 
 upon two causes, the command of the work over the point to 
 be attained, and the direction of the ground with respect to 
 the lines by which it is swept. 
 
 692.. .As to the command of the work over the exterio? 
 ground, it has already been shown that motives of economy 
 restrict it, in most cases, within very narrow limits, where to 
 obtain it artificial embankments have to be employed. To 
 augment, therefore, in the greatest degree this element of the 
 defence, advantage should he taken of the natural features of 
 
 the locality, by placing tin' principal lines, from which the ex- 
 terior ground can he seen, on the most commanding or highest 
 points of the site. If, with this position given to the principal 
 lines, the ground swept falls, or slopes toward them, the most 
 favorable combination for an efficacious plunging lire will he 
 obtaipedj for, with this direction of the ground, the enemy 
 will meet with far greater difficulty, to put himself under shel- 
 ter by his works, than where the ground falls, or slopes from 
 the line by which it is swept ; as the surface, in the latter 
 case, descending in the rear of the cover thrown up by the 
 
 
INFLUENCE OF tBBEGl LABTTIEB OF BITE. 233 
 
 enemy, will be screened to a greater extent than in the*former, 
 where it rises in tlio rear of the cover. 
 
 693. ..The general rule, therefore, which the engineer is to 
 take as a guide, in order to satisfy the condition of bringing 
 the exterior ground under an efficacious fire from the work, is 
 to plaa the principal lines of his work on tfu most command- 
 ing point* of th< site, ami in such directions as to brirftj the 
 anterior ground to b< swept in a position sloping toward these 
 limes; and this will generally be best effected by placing the 
 salient points of the work on the most commanding and salient 
 points of the site ; as, in this position of the salients, the fa 
 which are usually the principal lines bearing on the exterior 
 ground, will occupy the salient and commanding portions of 
 the site, whilst the re-entering, being thrown on the re-enter- 
 ing and lower portions of the lite, Will be in the best position 
 for sweeping the ground immediately in advance of the fa 
 and, at the same time, they will he masked by the faces from 
 the enemy's view, and thus preserved from serious injury up 
 to the moment when their action may he rendered most effec- 
 tive; that i> when the enemy, despite the fire from the faces, 
 has bucci eded in plauting himself upon points on which this 
 lire cannot longei he brought to hear. 
 
 • ;:» }...•_'<!. The condition of leaving no point of the defences 
 unguarded by the fire, will depend, in a great degree, for it* 
 fulfillment on the same rule as the preceding. But wl 
 both conditions cannot bi 1, the distant defence should 
 
 be sacrificed to the near, as upon the latter the more or ]. 
 obstinacy of resistance depends, since the lire of the work i 
 the action of tin . are the more effective as the point 
 
 guarded i* the nearer to the .. 
 
 d. The condition that the troops and ' within 
 
 the d shall he sheltered from the enemy's fire, from all 
 
 manding points without, will depend uj 
 tions of the principal lin< s and the < omraand 
 
 point.-; and as far, ' i i he done, without sacri- 
 
 ficing either of tl mportant conditi 
 
 30 
 
234 . INFLUENCE OF IKKl '.11 VRITIKS OF Mil:. 
 
 the plan of tin- work should be bo arranged that the principal 
 linos shall present themselves in the most favorable direction 
 to tlir exterior ground to avoid plnnging, enfilading or reverse 
 views npon their terrepteina from any point of it. 
 
 o':W>...To effect these objects, when the work is in the vicinity 
 of commanding heights within cannon range, and the crests ol 
 these heights, as seen from the work, present a nearly horizon- 
 tal outline, the principal lines of the work, fronting the heights; 
 should receive a direction as nearly parallel as practicable to 
 that of the commanding crests; when the outline of the crests 
 presents a nearly continuous line, but one which declines or 
 slopes toward the site of the work, the principal lines toward 
 the height should receive a direction converging toward the 
 point where the line of the crests, as seen, if prolonged would 
 join the site. 
 
 The reasons for the positions assigned to the principal lines, 
 in these cases respectively, may not, at a first glance, he ob* 
 vious; hut, by examining the relative positions of the crests 
 of the heights and of the principal lines, as here laid down, it 
 will, without difficulty, he seen that they can be brought in 
 the same plane, and the latter he so placed as to give a nearly 
 uniform command to the parapets of the principal lines over 
 the site ; and that by keeping the tenvplcins of these lines in 
 planes parallel to the one in which the crests of the heights 
 and those of the parapets are held, and at suitable levels below 
 it, the parapets will he made to cover the tenvplcins from the 
 fire of the heights in the simplest manlier. 
 
 G97...T11C foregoing general methods, for determining the 
 direction of the principal lines fronting commanding heights, 
 so as to cover from direct fire, in the easiest manner, by their 
 parapets, the space to the rear occupied by the troops and 
 materiel, present, at the same time, the simplest, cases of the 
 adaptation of the plan of a work to the features of the locality, 
 to subserve the object in view. In most cases, all that can he 
 done is to avoid giving such directions to any of the principal 
 lines as shall he favorable to enfilading or reverse views of the 
 
' . INFLUENCE OF IRREGULARITIES OF SITE. 235 
 
 enemy ; which may be effected by so placing them that their 
 prolongations shall fall on points where the enemy pannol 
 till >1 ish his works; or, on those which, If occupied by him, will 
 afford disadvantageous positions for bis batteries, cither for 
 enfilading or reverse fires. 
 
 G9S...I)uiu mi vi of I'kkmankm Works. The greater im- 
 portance of so adapting the plan and command of permanent 
 works to the features of irregular sites as to satisfy the condi- 
 tions of sweeping, thoroughly, by their fire all approaches ex- 
 terior to the defences, and completely flanking the latter, sel- 
 dom places it in the power of the Engineer to fulfil the condi- 
 tion of withdrawing the interior of the defences from either 
 enfilading or reverse views by a modification of either the 
 plan or the command. To shelter the terrepleins which would 
 be exposed to these tire.-, as well a> such as would be attained 
 by a plunging lire in front. resoW must be had to the usual 
 expedients of defilement ; that is, giving to the terrepleins 
 such positions with respect to their parapets that, the troops 
 and materiel upon them will be screened from a plunging fire 
 in front, by the parapets; and, when the terrepleins are 
 
 1 to either enfilading or reverse view.-, so placing earthen 
 traverses or other masks, as to intercept these views, and cover 
 the troops, etc., from the enemy*.- projectiles. 
 
 699.. .The defilement of permanent works, like that of field- 
 works, proposes the same end, and employs nearly the same 
 means. They differ mainly in their practical details; the lat- 
 ter being reduced to a simple practical operation on the held, 
 whilst the former, from the usually greater complexity of the 
 arrangements of permanent defences, requires the aid of tnath- 
 itical science, and demands results of i xtrem< 
 
 "T00...For the solution of all probl the defileini 
 
 nanent works, th< nires: 1st. The limit 
 
 ire may 
 - - uncertain as to I. 2d. The pre- 
 
 sume within this limit that the enemy up 
 
 to bring npon the w 
 
236 iMi.riM i: OF ikin.cri.AKiiii CS OF SITE. 
 
 rate topographical map di all the ground within the above 
 limil 76D by its horizontal curves referred to a plane of 
 
 comparison. 4th. The magiBtrale and interior crests of the 
 works, as either definitively or approximately arranged, re* 
 ferred to the same plane. 
 
 701. ..The limits beyond which the enemy's tire, from the 
 usual siege guns, may be disregarded, owing to tin- uncertainty 
 of long ranges, are L,500 yards, where the work is exposed 
 only to a direct, or front fire ; and 2,000 yards, when open to 
 a reverse fire. When the terrepleins, therefore, are covered, 
 either by their parapets or other means, from batteries at the>e 
 distances, they may be considered as offering shelters suffi- 
 ciently secure for the troops, etc., upon them. 
 
 702...H may happen that there are points beyond these limits, 
 but within the extreme rringe of siege gun.'-, which, from their 
 positions, it would not he safe to disregard; hut these will form 
 exceptional cases, and, when they occur, will be treated in the 
 same manner as those within the limits. 
 
 703.. .The surface embraced within the limits and the line of 
 defences, may be divided into three zones: one lying between 
 the limits and the position of the first parallel of the attack, 
 which is usually 600 yards from the salients of the line of de- 
 fences; the second between the positions of the first and second 
 parallels, or to a line within about 300 yards of the salients 
 just mentioned ; the third between the positions of the Becond 
 and third parallels, or up to within 60 yards of the salients. 
 In any position that the enemy can take up tor his batteries, 
 Within the first zone, it is usually estimated that he will not 
 throw up any parapet with a greater command than 10 feet 
 over the ground on which it is placed. Granting this, the 
 muzzles of his guns, behind the parapets, will not be raised 
 higher than 6 feet above- the natural surface ; so that, assum- 
 ing the surface of this first zone to be raised (! feet above its 
 true position, this may be regarded as the limit, vertically, 
 within which the enemy's lines of fire will be restricted ; and, 
 therefore, if the interior of the defences is covered from the 
 
TXFiJiM i: OF iKKE<;ri..\i;rrn:s of site. 237 
 
 fire -within this limit, the troops, etc., will be secure. Tliat the 
 enemy will not, in all likelihood, elevate his guns above thii 
 limit will seem probable, when it is taken into consideration 
 that any advantage lie might derive from doing so would not 
 be commensurate to the labor it would cost him. For, sup- 
 pose the enemy to have taken op a position for an enfilading 
 battery at 1,000 yards from any salient, to enfilade one of its 
 t'aees of the length of 100 yards; and that lie should decide 
 upon raising his gnns «3 feet, or one yard above the limit just 
 laid down; a simple proportion will show that, hy this increase 
 in the height of his battery, he will he ahle to attain a point 
 at the farther end of tlie face only 3.<> inches lower than he 
 would have done in the position of the assigned limit; an ad- 
 vantage which, considering the uncertainty of the fire at the 
 imed ranges, would hardly compensate the additional labor 
 
 of giving to his works the additional command. 
 
 704... In the zone between the first and second parallels, the 
 limit may ho reduced to 4m feet, tor at this distance from the 
 defences their fire is s<> destructive and certain that the enemy 
 cannot, without great loss of life and time, raise the parapet 
 of his batteries higher than 8 feet above the natural surface. 
 
 705... From the third lone, the musketry of the enemy may 
 he brought t<> hear upon the defence- ; and. from this position, 
 during sortie- from the defence-, or at any other opportune 
 moment when their tire is not active, the enemy might mount 
 on the parapet of his trenches, ami from there deliver his tire. 
 This would bring his line of fire about 1" feet above the na- 
 tural surface. The limit, vertically, of tl, may, th< 
 fore, he assumed at 10 feel above the natural surfs 
 
 706.. .The limits of the dangerous ground exterior to the line 
 of d( may he marked off on the topographical map of 
 
 the site, PI. 7. Km. 1. by drawing lines concentric with the 
 line ting the most advanced 
 
 and at tl m it of 1,500 OF 
 
 iic tire may lie brought to hear on the front oi 
 yards: 300 \ .ml- : ami 6< ' J ards; and tl 
 
238 l.M'i.ri:N< i; OF EBBSGULABITIES OF BITE. 
 
 once? of the horizontal curves of the ground, within the zones 
 thus marked off, to be increased <> feel in the lirst; 4.5 feet in 
 the second; and LO feet in the third. 
 
 707...In the defilement of each part, separately, of the line 
 of defences, those portions alone of these zones should be re- 
 garded as dangerous which are embraced within arc.-, or other 
 lines drawn at the foregoing distances from the salients, or the 
 laces of the ]>art to be defiled. It may also happen that, within 
 the limits of dangerous ground for one portion of the line of 
 defences, there may be other portions which, from their posi- 
 tion, may mask the portion to he defiled from all the danger- 
 ous points beyond them ; in which case the points thus shut 
 off need not be regarded, in effecting the operations of de- 
 filement. If, for example, PI. 7, Fig. 1, the limits of danger- 
 ous ground for the demilune A being marked oh", it is found 
 that the demilune B masks the demilune A from all fire that 
 might come from the ground beyond B ; then this portion of 
 the zones of danger need not be regarded in defiling A. To 
 ascertain this point, it will be only necessary to conceive a 
 right line to be so moved as to rest in each of its positions 
 upon a point of the interior crest of .1 and on one of B j and 
 if this line, in all its positions, passes above the surface of the 
 dangerous zones beyond B, then will B serve as a mask for .1. 
 
 708. ..In covering masonry from the enemy's artillery, 800 
 yards is usually regarded as the longest range at which de- 
 structive effects can be produced ; and, also, that within this 
 distance the angle of incidence of the ball on the surface must 
 be greater than 45°, to do serious injury to it. 
 
 709.. 4*i the defilement of works of limited interior capacity, 
 as, for example, the redoubt of the reentering place of arms, 
 the double caponniere, and the like, which are, moreover, not 
 habitually occupied by troops, the extreme limits may be re- 
 duced to l,iMiil ,,r l.-jmi yards. 
 
 710... Within the limits of the zones of danger, positions may 
 be found for direct or front, for reverse, and for enfilading tire. 
 If the tw r o faces, for example, of a work be prolonged to in- 
 
iNFi.rr.Ni'i: OF 11:1:1 OUL \i:n n a Of sin:. 239 
 
 tersect the extreme limit ofdangerous ground, the Bector which 
 they embrace may be termed the limits of direct or front fire f 
 since, from every position that can be taken up within this 
 sector, a direct fire alone can be brought to bear upon the two 
 faces. The two sectors which lie adjacent to this may be 
 termed the limits of lateral or reverse fire, since they afford 
 positions from which a reverse fire can be obtained againsl 
 one of the faces, and a front fire upon the other. It is also 
 only -within these last limits thai positions for enfilading the 
 terrepleins of the faces can he obtained. 
 
 711. ..The problems of defilement which present themselves 
 for solution may embrace one or more of th- - in any 
 
 example; depending upon the relative positions of the interior 
 crest of the work to he defiled, and of the dangerous ground 
 embraced within the foregoihg limits. In the case of only di- 
 rect fire, the terrepleins can he screened by their parapets 
 alone; in that of a reverse tire on one face alone, its terre- 
 plein, in some cases, may be screened by a suitable" position 
 given to the parapet of the other; where both are exposed to 
 this fire, one or more traverses must be resorted to as a screen; 
 against an enfilading fire on one face alone, a portion of the 
 parapet of the ether, near the salient, may he a sufficient pro- 
 tection in Borne cases : but, for the most part, traverses, placed 
 across the terreplein, will he the only remedy. 
 
 712... It does not cotne within the ^mjir of thi- summary t<> 
 examine the many cases of defilement which may arise from 
 irregularities in the site ; those alone will he discussed which 
 are of most ordinary occurrence, and which require for their 
 solution the usual geometrical constructions involved in tan- 
 gent and .-cant planes and other surfaces, to a surface defined 
 
 by the projection of its horizontal curve.-. The i hich 
 
 will here find their application may he arranged under two 
 head-: 1st, the plan and command of a work being definitely 
 decided upon, to ascertain t 1 portions of 'he z. >n. 
 
 danger from which any description of tire can he brought to 
 hear upon it.- terrepl ins, and to defile them from it ; i'd, the 
 
240 INFLUENCE OF IRREGULARITIES OF SITE. 
 
 plan of a work being definitely fixed, but its command only 
 approximately within certain limits, to ascertain the eaei 
 method of defiling the terrepleins of the work by varying the 
 command, or position of the interior crest, within the assigned 
 
 limits. 
 
 !T13...Pbob. 1, Pl. 7, Fio. 2. The command or position of 
 
 ih' int< rior <■/■< *Ay of the facts of a work b< ing v'-v< <L to aso r- 
 tain tin dangerous points on th< exterior, and to defiU its t> r- 
 r&plein from t/ccse points. 
 Let a b, a c, be the projections of the given crest; and the 
 
 curves (28. 0), (29.0), etc., those of the natural surface. 
 
 Prolong outward to c and d, the faces ; construct the scales 
 of declivity of the two lines ae, ad; and, from them, the 
 scale of declivity, ef, of their plane. From the salients, sup- 
 posing an arc to be described with a radius of 1,500 yards, the 
 dangerous ground will be included between it and the two 
 faces of the work. Now, if the plane of the interior crests, of 
 which ef is the scale of declivity, be indefinitely extended; 
 and its intersection with the surface parallel to the natural 
 surface and 0" feet above it be found, it is evident that the por- 
 tion of this raised surface which lies below the plane may bg 
 disregarded, as no fire from it can have a plunge upon the in- 
 terior of the work. But, from every point of the surface 
 above the plane, a plunging fire can be brought to bear on the 
 terreplein. Having drawn the horizontals of the plane ef, 
 and found their intersections with the corresponding horizon- 
 tals of the raised surface (which last will be given by adding 
 feet, or 2 yards, to the references of the curves of the ground), 
 of which xy z is the projection. That portion of the surface. 
 which lies above this curve will alone have a plunging tire 
 upon the work, and will be the only portion for which defile- 
 ment will be necessary. 
 
 Now, as this intersection falls entirely within the angle d a 
 e of the faces prolonged, or within the limits of front fire, it is 
 evident that the terrepleins will require to be defiled only 
 from direct fire. 
 
INFLUENCE OF IRREGULARITIES 01 SHE. 241 
 
 To effect this, let a plane be* passed through the face, J, a d, 
 of the work, and tangent to the raised surface above x yz. 
 Tin's plane will pass above all the dangerous ground, excepl at 
 its poinjfc of contact with it; and, being extended -back from 
 the face within the work, it is clear, if the terreplein of this 
 face be so taken with respect to this plane that no point of it 
 shall he less than 8 feel below the plane, that then every point 
 of the terreplein will be screened tVom a plunging fire by the 
 ■parapet of the lace a h. Now, if the same series of operations 
 be gone through with for the face c a e, then will its terreplein 
 be defiled in Like manner; and thus the defilement of the 
 whole work be completed for this ease. 
 
 The tangent planes which satisfy the above condition are 
 termed Planet of Direct Defilement, and they may be defined 
 as planes which, passed through tin interior crest of apwrape% 
 learn at least 6 feet below them ail the dangerous ground <>f 
 front Jire, and pass at lea/si 8 feet above every point of ilu t< r- 
 replein behind tht parapet. 
 
 The terrepleins are usually parallel to their respective plai 
 of direct defilement, and 8 feet below them. 13ut when the 
 declivity of the plane of defilement exceeds 1-25, then the teiv 
 replein, if it is to receive cannon, must be kept within this 
 limit. 
 
 In the Fig. •_', the references are put down in yards. The 
 tangent plane through b a d is determined in the usual man- 
 ner, by finding the horizontal (in th 30.0), among all 
 those drawn to the curve- of the raised surface) which ma 
 the mimimum angle with b <L The line /< /, perpendicular to 
 this horizontal, is the Bcale of declivity of this plane; and the 
 point J?, that of contact. The Line k I is, in like manner, the 
 of declivity of the other plane, and <> its point of conj 
 
 71 4 — It might happen, from the steepness of the terrepleins, 
 that the reentering, or gutter, formed at their intersection, 
 would be inconvenient, and it would, thi •• desirable 
 
 to have this portion raised, when it can be done without 
 posure to a plunging lire. This, in m< 
 
242 l.MIM.N.i 01 LRBBGULABrnSS >.| SITE. 
 
 iii this way. It will be seen, from Bn inspection of the V 
 that the points o and p are the only ones from which the 
 enemy's fire pass* - i jcactly al 8 feet above all the points of the 
 respective^ terrepleins determined by the tangent planes; and 
 that if, from these points, lines of fire, o a r and p a «, be 
 drawn, every other line of fire through </, from the ground in 
 the angle p a o, will pass more than 8 feet abov^e the portion 
 of the terrepleins embraced in the angle s a r, since the 
 ground within the exterior angle lies below the tangent planes. 
 If, then, a be taken as the verliex of a cone, tin* elements of 
 which arc tangent to the raised surface within the angle p a <>, 
 and if these elements be prolonged within the work, their pro- 
 longation will form a cone of lines of fire, which will pass 
 more than 8 feet above the terrepleins. If these last, there* 
 fore, be connected by a surface parallel to this cone, and 8 
 feet below it, this surface may be taken as the portion of the 
 tefreplein which, connecting the two plane portions, will 
 remedy the inconvenience pointed out. 
 
 715...P&OB. 2, Fig. 8. The data being the sanu as i» the 
 preceding oase, and thewoflc being exposed to both direct and 
 reverse vu mw, to oov'er its interior from thest vi* ws. 
 
 Suppose the plane of the interior crest of the faces extended 
 within the limits, and its intersection with the dangerous 
 grbund determined, as in the preceding case; and let x y 0, vi 
 n and J? q r be the curves of this intersection. 
 
 The face a b will be exposed to direct fire alone from the 
 ground above the two curves, x y z and m n 0, and to reverse 
 fire from that above the curvey q r. In like manner, the 
 face a c will he exposed to direct fire from X ;/ 3 and p q r, 
 and to re\ erse fire from m » o. 
 
 The defilement of each face, from the direct fire, will be 
 effected jprecrsely in the same way as in the preceding problem, 
 The lines // i and k I are the scales of declivity of the planes 
 of direct defilement of the faces respectively 1 . 
 
 For the reverse defilement, a plane is passed through a b, 
 tangent to the surface above p q >• ; and one through a <\ tan- 
 
INFLUENCE OF IKIM.i ;! I.AKI'l IKS OF SITE. 243 
 
 gent to the surface above //, ?i 0, and their line of intersection 
 a a' found. The line u v is the scale of declivity of one of 
 these planes, termed a Plane of Revem Defilement^ and s t 
 that of the other. 
 
 Now, if a traverse is so placed that its crest shall occupy 
 the position of the line a a', it will coverall between it and 
 the two faces, as high as the interior crests, from the reverse 
 fire on each side. But as it is desirable to have the troops, 
 when «m the banquettes, screened from this fire, the crest of 
 the traverse should he raised from 18 inches to 2 leet ah 
 the line Q <t\ to effect this. 
 
 The traverse should extend so far toward the gorge of the 
 work that the entire line of each face shall be covered by it. 
 To determine its length with this condition, lines are drawn 
 from the extreme point, b and c, of the faces, tangent to the 
 curves m n <> ami p <j /•, and their points of intersection with 
 narked; the one that falls farthest from the salient, will 
 evidently give the required length. 
 
 If the line a a', should fall so near either of the faces that 
 . if placed along it, would incommode the service 
 of that part of work, it will be best to place it.- eiv.-t in the 
 ■vertical plane a a" of the capital of the work. When M 
 placed, the intersection of tin.- vertical plane with each of the 
 planes of reverse defilement must he found, and the crest of 
 the traverse he taken i 8 inches above the one that lies highest. 
 
 716.. .The position of th< ifthetra rmined 
 
 by either of the preceding methods, will he in a vertical plane 
 passing through the salient </ of the work. Prom the thici 
 and slopes which travetWi usually receive, they would ordi- 
 narily, if placed in this position, take up ail the inter' 
 within the salient, and have no room there for disposit 
 either for artillery or musketry. To .prevent thi ik is 
 
 made in the direction of the ie point on | 
 
 plane through the salient, from which it \> «. 
 
 .:• tron i | 
 
 cient room will b In th 
 
2-14 ini ill N< i: OF IKEEOTJl \i:mi:s OF BITE. 
 
 which illustrates this arrangement, tlie traverse is withdrawn 
 far enough from the salient to leave room for a barbette bat- 
 tery for several gun:-. 
 
 The laee upon which the traverse is directed, will be deter- 
 mined by the condition of covering both faces in the most 
 effective manner, by the position taken for the traverse. 
 
 717. ..The cross section of traverses for permanent works is 
 similar to those used in field-works. The top of the traverse 1 
 receives a slight slope each way from the crest to the sides. 
 The thickness at top is from 12 to 20 feet, to render it shot- 
 proof. The sides take the natural slope from the top, either to 
 their intersections with the planes of direct defilement or to 
 the terreplein. If. to gain interior space, these slopes are ter- 
 minated at the planes of direct defilement, then the portions 
 of the traverse below these planes are made more steep, and 
 the earth supported by retaining walls. The top of the trav- 
 erse, where it joins the parapet, being higher than the superior 
 slope, is run out above this slope, upon which the side slopes 
 tall ; its extremity terminates in the plane of the exterior slope, 
 extended above the exterior crest. 
 
 718. ..Traverses may be arranged for bomb-proof shelters 
 and musketry defence, by throwing a bomb-] .roof arch be- 
 tween the side retaining walls, and piercing the wall hearing 
 on the portion of the terreplein which will first fall into the 
 enemy's power with loop-holes. 
 
 7l:i...\\'hen from any circumstance, a single traverse cannot 
 
 be used, for reverse defilement, resort must he had to several, 
 which should he so combined that no line of lire can pene- 
 trate between their extremities to attain any point which they 
 should cover. The examples of like combinations given in 
 the Front, will readily suggest the manner of making others^ 
 of which farther illustrations will be found in the following 
 ease. 
 
 720. ..Where a demilune is arranged with a redoubt, a tra- 
 verse placed in its salient cannot be extended farther hack 
 than the counterscarp of the redoubt, and an -open space, 
 
INFLUENCE OF IRREGULARITIES 0¥ BITE. 245 
 
 therefore, will lie left at the ditch, through which a reverse 
 fire would attain that portion of either face which is not cov 
 ered either by the traverse in the salient or by the parapet of 
 the redoubt To cover the part thus exposed, it will he n< 
 sarv to place one or more traverses which, in combination with 
 the one in the salient and the parapet of the redoubt, shall 
 subserve this end. 
 
 To simplify the case, let the face a <?, PI. 7. Fig. 5, he the 
 one exposed, and let the point x be one the fire of which is 
 most dangerous. Having, in the first place, arranged the tra- 
 verse t. as in the last example, and drawn the two lines of fire, 
 b and x d, from the point ./% through the extremity of the 
 traverse and the top of the parapet of the redoubt at the 
 
 salient, the length, h <L of the face intercepted between these 
 lines will he the part to he covered. It' a second traverse, 1\ 
 he placed across the terreplein of the other face of the demi- 
 lune, and in a position such that one of its ends shall real on 
 ,/• />. and the other on x </. it will evidently cover the portion 
 
 bd. 
 
 721. ..In selecting the positions of several Combined trave: 
 attention muBt be given to avoid those where, if one be placed) 
 the enemy would lind shelter behind it from the fire in the 
 rear. Tn the example just taken, the slope of f. toward the 
 
 salient, should be swept by the fire from the rear, through the 
 
 redoubt ditch ; the Hke slope of t should he swept by a por- 
 tion of the redoubt face mar it- salient : and neither &0 Pail as 
 to have tin sp ace behind it masked from tire by the one t 
 rear. 
 
 722...Trav< rs< - usually pn Bent not only the : ,,n 
 
 of all problen i rse and enfilading defilement, hut. afford- 
 
 ing the means of rendering the command independent of 
 tire from without, they enable the engineer t.. regulate this 
 
 ly with a view t.. the effect which lie d( 
 attain by his own fire. From the - ■ , r the ,r 
 
 "ion. tra ,iy. a- in tic f narrow ten 
 
 like those of the Inne with a 
 
246 infi i ! n< 1: OF rRREGULAMTTRS OF BIT*. 
 
 redoubt, be inconvenient, 1 >< >tli from embarrassing the commu- 
 nications ami from taking up ground that may be wanted for 
 batteries. 
 
 r23...Pa08. ■'*. Tht plan of a bastion being definitively fioaed\ 
 and cm point of it* comma ml approximately, A< <hjil< fh< 
 workinthi most advantageous manner, by nJii/t'nty tlie post* 
 fion <>/ Us interior crest within certain Hunt*. 
 
 Let Fig. 6 be tke plan of the work, and a the salient, tin* 
 command of which can be varied within certain limits, with- 
 out impairing any of the other conditions; arid let the danger* 
 ous ground be embraced within the arc m », at 1,500 yards 
 from a, and the lines a il and a o supposed drawn from a, 
 through covering masses on the right and left of the work. 
 
 The front limits of defilement in this case are embraced 
 within the sector m a&i / and the lateral limits within the 
 other two, m a u and n a v. Now, the most favorable ease of 
 defilement here will be that, where a plane, containing a taken 
 within its extreme positions, shall pass above all the exterior 
 ground, and give such a command to the interior crest through- 
 out, when held in it, as shall satisfy the other conditions of de- 
 fence. To ascertain the existence of such a plane, let a be 
 taken as the vertex of a cone which envelops all the danger- 
 ous ground, any plane tangent to this cone will satisfy the 
 condition of defilement, ami it will, therefore, only be necessary 
 to find whether any one of these planes of defilement will satisfy 
 the other, of giving the points />, *'. d and <■ a suitable command. 
 If no such plane can be obtained, the next most favorable case 
 will be to find one that shall satisfy all the requisite conditions 
 of command, and intersect the ground only within the front 
 limits. In this case it is clear, from tin- position of this plane, 
 if the interior crests are held in it, that the interior of the 
 work will be exposed only to the direct fire from that portion 
 of the ground which lies above the plane. 
 
 Let xy z be the curve of intersection of the plane with the 
 ground, found in the usual way. Through the faces a b and a 
 d, let planes of direct defilement be passed ; the terrepleins of 
 
IM i i I n< r 01 11:1:1 (.! I.AKITIKS <>K 81TB. L'I7 
 
 the faces being held parallel to them Will be covered by their 
 respective parapets from all plunging fire. But, in order that 
 the planes of defilement of the faces shall also defile the flanks, 
 it is necessary that each flank be placed in the plane of defile- 
 ment of the adjacenl face, and its tenreplein in that of the tor- 
 replein of.the face. Now, in giving the interior crests of the 
 flank- these new positions, they will lie below the plane that 
 contains the curve X y s, and ill' which the mterior crests of 
 the faces lie. This being the case, it may happen that the 
 parapet of one of the flanks will not cover the opposite face 
 from reverse fire, coming from the lateral limits opposite the 
 flank. Tn this contingency it will be necessary, in order to 
 cover the lace, to place the flank in the plane of the curve ,r y 
 .7, as this plane defiles from the lateral limits: but, in doing 
 this, the flank <1 < . for example, will be exposed, in its turn, to 
 the ground above s»ys/ and to cover it, the only remedy is 
 to erect a traverse, at some suitable point, which shall inter- 
 cept all this dangerous fire. The least inconvenient position 
 for the traverse will usually be at the shoulder angle. From 
 this point, it must extend so far hack as to intercept all fire 
 from above x y ~. botb on the terrepleina of the flank and cur- 
 tain, where they unite, and be high enough to screen the tro 
 on the banquette. 
 
 If the defilement cannot be effected by either of these pro- 
 -, there remains no other means than, having fiivt defi- 
 nitely fixed the command, to devide the bastion by a trav< 
 either along its capital or some other convenient direction, 
 and. having given it a suitable height, t<> covm each portion 
 from direct tire by the usual method. 
 
 7-1. ..Tin- foregoing problemi embrace in their solution all 
 of the more ordinarv cases of defilement, and suL r L r c~t the ,. 
 
 to be followed in treating Others. In all 'de- 
 
 ment of combined works, like the enceinte mid it- outwo 
 . it must h'- home in mind that the advanced \\ , 
 which, from their | must first 'fall into the i 
 
 power, become thus a portion of 4he dangerous ground for 
 
248 IM-I.I l..\i I. o|' lKKl.ol I.AKllll.S OF Mil:. 
 
 works more retired, and which must also be held after the fall 
 of tin- others. The retired works, under such circumstaa 
 must be defiled from the advanced; their planes of defilement 
 being made to pass from •". feel to l.."> feel above tin- portion of 
 the advanced work on which it is presumed the enemy may 
 make a lodgment, ami which, from its position, may be re- 
 garded as the most dangerous to tin- retired work, it is ac- 
 cording to this role that the redoubt of the reentering place <>t' 
 arms is defiled from tin- parapets of the two adjacent demi- 
 lunes; its plane i>t' defilement extended outward, passing at ."> 
 feel above the salients of these works. The tenaille, in like 
 manner, is defiled from the upper terreplein of the demilune 
 redoubt, as the tenaille must, he held after the enemy has 
 established himself on this terreplein. For like reasons, the 
 nmre retired portions of the covered-ways are defiled from the 
 enemy's lodgments on the glacis of the demilune salient place 
 of arms. 
 
 7i ; r>... Where a work has considerable command, and is open 
 at the gorge, like the cavalier retrenchments, for example, ami 
 the works in its rear do not mask its interior from reverse lire, 
 it may he necessary to place the traverse, termed aparadosi 
 acrof replein at the gorge, giving it sufficient height 
 
 to subserve the end in view. 
 
 T26...The methods of defilement here laid down are those 
 now followed by engineers. They unite mathematical accu- 
 racy in results, with great simplicity of detail; and render the 
 defilement altogether secondary to the other conditions of de- 
 fence, upon which the plan and command are made essentially 
 to depend. Before they were adopted, the results of the 
 method then followed were, in most respects, like those ob- 
 tained in the practical operations for defiling lield-works. A 
 line, the position of which was determined by a series of trials, 
 
 having for their objeel to obtain the most satisfactory results, 
 both as to the economy oi the requisite embankments and the 
 best disposition of command of the various parts at or in rear 
 Of the gorge of the work to b% defiled; this position coinciding 
 
INFLUENCE OF IRKFOn.AKTTTl s OF STTK. 24f) 
 
 with the natural Burface, or being above or beneath it, as the 
 case required. Througli this line a plane was passed tangent 
 to the dangerous ground. This plane, termed, as in field de- 
 filement, a Rampant Plane, was taken as the artiiicial site of 
 the work, in reference to which the relative command of all 
 the ] >arts was arranged as upon a horizontal site. Or, in other 
 words, the result was nearly the same as if the works had been 
 arranged on a horizontal site, and then the whole combination 
 turned aronnd some fixed line of this site, until it was brought 
 into the position of the required rampant plane. The defects 
 of this method are evident at a glance. It preserves the rela- 
 tions of defence of the various works the same as in a horizon- 
 tal site; but it. to a great extent, leaves out of consideration 
 Ae bearing of the command on the exterior ground, and, in 
 many cases, may lead to excessive excavations and embank- 
 ments which the methods now followed enable the engin 
 for the most part, to avoid. 
 
 7_7...Ki MAi.-K-. In the preceding discussions it will be ob- 
 served that the limits of defilement, horizontally, have been 
 based Upon the range and presumed accuracy of tire of artil- 
 lery and small arms before the changes which, within a few 
 years back, have taken place in both these particulars, and 
 which — from tin- zeal ami intelligence with which experiments 
 are now being carried on, in every part of the civilized world. 
 on the forms of cannon and projectiles and the quality of 
 powder — will, in all probability, be extended and lead to still 
 more remarkable results. These improvements, however, will 
 have no other effect upon the rules and modes of d< ill' I 
 now in use than to change the limit-, hi rrc- 
 
 spond with the ii of projectiles. 80 far ai 
 
 improvement in the accuracy of tire is concerned, it will ren- 
 der a strict defilement of all parts of the interior of a work] 
 more imperative, and will lead engineers t.. resort I 
 
 ins by which the troo be hidden from 
 
 an enemy's \ ;< W within the extreme 1 
 to t 1 // limits, th( 
 
 32 
 
250 MINES. 
 
 for changing those now established. "When it is, also, taken 
 into consideration that the relative command and plunge of 
 heights decrease with their distance from the work defiled, and 
 also, that the accuracy of aim is greatly affected by the same 
 cause, it is questionable whether any considerable extension 
 of the limits hitherto laid down will be necessary, except in 
 marked cases of locality. 
 
 MINES. 
 
 728.. .The subject of mines admits of a division into five parts : 
 
 1st. The nomenclature. 
 
 2d. The results of experiments, and the theory founded on 
 them. 
 
 3d. The manner of using mines in the attack and defence. 
 
 4th. The conditions to which mines should be subjected in 
 their arrangement and uses. 
 
 5th. The construction or details of the practical operations. 
 
 To these may be added a sixth part, comprising the uses of 
 mines in temporary works. 
 
 729. ..Nomenclature. The term mine is applied both to the 
 underground excavations charged with powder for the purpose 
 of producing an external explosion, and to the communications 
 which lead to these exra vat ions. 
 
 The excavation in which the charge of powder is lodged is 
 termed the chamber. The pit formed by the explosion is 
 termed the crater. 
 
 The form of the crater in ordinary soils has not been exactly 
 ascertained. The only use of the exact determination of this 
 form would be to calculate precisely the quantity of earth 
 
v MrNE8. 251 
 
 thrown from the crater, and by that moans to proportion the 
 charge to the effect to be produced. Different figures have 
 been assigned by engineers, to this solid; some assuming it to 
 he a cone, of which the centre of the powder was taken as tile 
 vertex; others, a paraboloid, of which die centre, of the pow- 
 der was the focus. To afford a uniform and simple rule for 
 calculating the volume of the crater, the solid, PL A. Fig. 3, 
 is assumed to be a truncated cone, the radius, d y of the lower 
 circle being one-half the radius,/? 5, of the upper circle. The 
 radius p b, of the upper circle is termed the craU r radius. The 
 line, o ]>, drawn from the centre of the powder perpendicular 
 to the surface where the explosion takes place, the line (f least 
 resistance. The line, q b t drawn from the same centre to any 
 point in the circumference of the upper circle, the radius of 
 explosion. 
 
 The term oommon /><<>" is applied to a crater when its radius 
 |iial to the line of least resistance. When the crater radius 
 is greater than the line of least resistance, the terms ,,,>,,- 
 oharged mine and globe of compression are used. When the 
 crater radius is less than the line of least resistance, the mine 
 is termed undercharged. A small mine with a line of least 
 n distance not greater than 9 leer, which is formed by sinking 
 a shaft from the surface of the ground, is termed a /">"/• 
 The term camoufiel is applied to small mines used to suffocate 
 the enemy's miner without producing an external explosion. 
 
 The underground communications required for the service 
 of mines are termed galleries. The galleries are either arched 
 communications of masonry, or else a framework and sheeting 
 of timber. The principal gallery immediately behind the 
 Counterscarp wall, is termed the counterscarp or magistral 
 A ry. An < nvt loping gall* ry is one parallel to the counterscarp 
 gallery, and at some ::" or 1" yards in adva 
 galleries leading outward from the counterscarp gallery are 
 
 The galleries which com 
 eral listening gallerii 
 
 uticular name- from tin ir size, as the 
 
-•"'- MIXES. 
 
 dual or grand galleriet, which are 6 feet high and <'» feet wide. 
 ( ommon galL /•/<*, •• " "3 
 
 ffalfgalltries, " U " « 3 " 
 
 Branch . " 3£ " " 2£ " 
 
 Small Branetiuj " >J\ * " 2 " 
 
 730...Expeeimewm. But little advance by experiment has 
 been made in the subject of mines, owing to the time, labor 
 and expense, which a prosecution of the subject demands ; and 
 the practice has, therefore, undergone but slight changes sinoe 
 the earliest introduction of thia means of attack and defence. 
 The following facts, drawn from observation, comprise almost 
 all that is at present known on the subject: 
 
 1st. Jn solid rock, an explosion causes the rock to split in 
 Various directions, and it' the charge is heavy, will break it 
 into small fragments, which are frequently thrown to a great 
 distance. 
 
 2d. In sand, the gazes seem to penetrate between the grains, 
 producing a crater of a regular form, the radius of the appei 
 circle of which is generally small in comparison with the 
 depth. I 
 
 3d. In ordinary tenacious soils, the first effect of the explo- 
 sion is to produce a rumbling noise, and a sensible trembling 
 of the earth around the mine to a Considerable distance; the 
 ground directly over the mine is next observed to rise in the 
 form of a spherical segment, which increases perceptibly until 
 the smoke' commences to issue forth around its base; the ex- 
 plosion outward follows immediately on this last change, the 
 earth, mingled with smoke and dame, being thrown upward 
 and outward, so as to assume a form something like a water- 
 spout ; part of the earth falling back into the crater and apart 
 without, forming a ridge around its mouth. 
 
 The two most remarkable features of the explosion are its 
 internal and external effects; the first producing the crater, 
 the second so disturbing the earth for a considerable distance 
 around the crater as to till up cavities, destroy galleries, etc., 
 
min 258 
 
 •within the sphere of its action; these effects extending farther 
 
 in a lateral than in a downward direction. 
 
 The charges and their effects do not follow the same ratio, 
 the last increasing less rapidly than the first. Experiment has 
 shown that the charges may even be increased one or two 
 pounds per 4 cubic yards, without increasing the crater radius; 
 the only effect of this increase of charge being to throw more 
 of the earth clear of the crater. 
 
 Prom experiments made on common mines, with a line of 
 Least resistance not exceeding l.~> feet, it has been ascertained 
 that the tenacity of the earth is completely destroyed around 
 the crater, to a distance equal to the line of least resistance, 
 and that empty galleries are broken in at a distance of. 
 and a halt* the same line. 
 
 In homogeneous soils, the resistance due to the tenacity of 
 the soil is nearly proportional to the mass. 
 
 It was lor a long time supposed by miners that a crater could 
 not be formed with a diameter greater than twice the line of 
 least resistance, with any eharjge; but the experiments of Be- 
 lidor have shown that, by successive augmentations of the 
 charge, tin- crater radius may be increased to six times this 
 line, but not much beyond ; that within this limit tin- ratio 
 the diameter- of the craters is nearly that of the square POOl 
 
 of the charges; and that galleries ean be destroyed by such 
 mines at distances of four times their line of hast resistai 
 [....Theory. The physico-mathematica] theory of mil 
 11 \i-ry imperfect, owing to the impracticability of a» 
 taining the exact effects of the explosion of powder in a 
 medium which is seldom ho and the i 
 
 which, arising from it.- tenacity, con 
 
 :i of tie only be arrived at by a ->\ 
 
 experiments made with mini, 
 ■in the lementary «i. formula 
 
 ■ nt in ns- . nine the charges for 
 
 mpirical, and their n - 
 only within the limits in which the} 
 
254 mi\ 
 
 meats. For most cases in practice, these approximations, are 
 near enough, and valuable as the only guides that the mine* 
 has to refer to. 
 
 ^32... The resistances which the gazes overcome are the weight 
 of the volume of earth thrown from the crater, the tenacity of 
 tin- medium, and the atmospheric pressure od the upper circle 
 of the crater. The two firsl are proportional to the ma- 
 earth thrown out. and the last to the upper surface of the 
 crater. To express the ratio of these resistances to the char 
 let us represent in any two mines by 
 
 c d, the charges; 
 
 /• /•'. the radii of the craters; 
 
 1 1\ the lines of least resistance; 
 
 d d\ the weight of the unit of volume of the two soils; 
 
 it n', the constants, which, multiplied into the weights, will 
 express the tenacities; 
 
 h //, the heights of the atmospheric columns reduced to the 
 
 densities a& the .-oils. 
 
 Whatever may be the form of the crater, its volume can he 
 expressed in terms of the surface of the upper circle, and 
 some fractional part of the line of lea>r resistance ; bo that 
 if we represent by 1 I and J. I' this fractional part of the line 
 
 of least resistance in the two cases, we shall have for the 
 expression of the two volumes: 
 
 7rr 2 x Land«V*X '' ; 
 
 m 
 
 and for their respective weights, 
 
 !!> 2 'x <1, and 77r '' 2 .'' x d ; 
 
 m in' 
 
 to express the tenacities we have, 
 
 a 2 
 
 ~ r _*ji, and£r! ld 'x n': 
 
 vi m' 
 
 and for the weights corresponding to the atmospheric pressures, 
 
 n r-/< <% and *?'*'& &. 
 From these expressions we obtain the proportions 
 
 c : d : : 0[(» + l) I + m //] : tl* [(n'+l) +1' m'hf\ 
 
mini -. 255 
 
 For the same soil, as m=7n', ?? — »', d=d', and h = h', tin's pro- 
 portion becomes 
 
 c : c". -y-(i+^h) : ^(r+i"iA'). 
 
 733. ..The relation between any two charges of mines in the 
 same soil, expressed by this proportion gives the means of ob- 
 taining the charge for any crater when, by experiment, the 
 crater formed by any known charge has been found, provided 
 the quantities n and // are known. Of the first, nothing defi- 
 nite is known but that it varies with the kind of soil. The 
 rod lias beet) assumed equal to 11 feet. This want of defi- 
 niteness in the value of these quantities has led to omitting 
 them in the proportion, when used for practical purposes, in 
 which case it takes the felTowmg form : 
 
 '[ \ : i r '* : v ¥ *. 
 
 T\\\> is termed the Mint r*a Ride, as it is used for calculating 
 tahles of charges for different soils ; and its results do not differ 
 materially from those of experiments* 
 Making l=l\ the proportion becomes 
 c . c . .r 2 . r *, 
 a proportion also differing but little from the results obtained 
 within the ordinary Limits of practice, when the lines of least 
 me for different chargi 
 734...Assumjng, as is the case in common mines, that the 
 craters are similar solids, then I ', $', \r '. r ; hence, 
 
 • : /' 
 another form of the H -■ d in calcu- 
 
 lating the tables of cl >r similar mrni 
 
 The manner in which this rule is applied to calculate cl 
 omtnon mine* the quantity of powder, y. in 
 
 pounds, required to throw up one cubic ys 
 
 mud by experiment. As the solid a trun- 
 
 ial to 1 ]■>'> / . ; the Hi,, 
 
 . the i olum< of tl line of L 
 
 ird, will be : ,, r 
 
256 minis. 
 
 11-6; this volnfne, multiplied by q, will give the charge in 
 
 pounds for this crater, but from the proportion e \ <■' ; ;/ :; '. ( ' 3 , 
 there obtains : 
 
 c: n-6 y ::/•'*: i :; . orc=li-6?Z 8 , 
 
 for the charge for a crater'whose line of least resistance is I. 
 
 ' ,7 M, chargt , M- r^/bn ./"/■ a .</''''. h K/n of least resista 
 cul„ this line, expressed in yards } tah ll-6>of tin result and 
 multiply it by the number of pounds required to throw out a 
 cubic yard of tJu soil in Question. 
 
 The following table expresses the values of g : 
 
 Lb*. Oz. 
 
 Light sandy earth 1 13 
 
 Hard sand 2 00 
 
 Common earth 1 10 
 
 Wet sand 2 2 
 
 Earth mixed with pebbles 2 8 
 
 Clay mixed with loam 2 8 
 
 Eock 3 10 
 
 735. ..As the Miner's "Rule is applicable only to common 
 mines, resort must be had to some other to And the charges for 
 overcharged and Undercharged mines. The formula in most 
 general use for these cases are those of Lebrun, a French engi- 
 neer; which, although not based on any satisfactory hypothesis, 
 nevertheless, coincide nearly in their results with those ob- 
 tained by experiments within ordinary limits. The hypothesis" 
 assumed to obtain these formula is as follows: Suppose two 
 craters, formed by two different charges, o and <■', with the same 
 line of least resistance, one giving a crater radius, ;•, equal to the 
 line of least resistance} the other a crater radius, Ji, greater, 
 the difference of the radii being R — r. Next, suppose the 
 charge 6 to belong to a common mine, of which the crater ra- 
 dius is r • r — /', being the difference of the radii of two craters 
 of the common mines of which the charges art' o and <■' ; then 
 the ratio of the two differences here expressed, arising from 
 the same increase, c' } of the charge c, will be constant under 
 
MINT-. 857 
 
 all circumstances of variation of soil, and of the lines of Least 
 resistance. Calling /f this constant ratio, there obtains: 
 
 }i—r_ t- # • 
 
 r' — r— h ' 
 
 assuming R=n r, this formula becomes 
 
 r(n— 1) _ jy- , 
 r' r — IX ) 
 
 <<=;.x(ra— i)+i; 
 
 but as f and r belong to similar craters, the "Miner's Rule 
 
 3 
 
 gives c = — : from this there obtain-. 
 
 The quantity, h". which enters into this expression 1 must be 
 ascertained by experiment, as indicated by the process fol- 
 lowed in obtaining the formula. From a comparison of a 
 number of experiments, the value of h' isr 
 *=c[6.91 n+0.09}*. 
 i36...The preceding method is also applied to find a formula 
 for the charges of undercharged mines. In this ease, R and 
 /■' being supposed less than /', L~~~^jr and hence c'— 
 
 The constant K in this case, ia determined from a result of 
 experiment; that if a certain charge of powder forms a com- 
 mon crater with a Line of least resistance I, the same charge 
 will not produce any external effect when the. line of I 
 
 i to 1| / or 7-4 / .• and, i 'ally, if a 
 
 charge produce! no external effect with a line of leasl 
 
 /. the same charge will form a common mine under a line 
 of ! 1-7 /. If. then, the charge </, by sup] 
 
 tion. ■• product sternal effect under the lint 
 
 Leasi . it will prod 'Ninon mine under a line 
 
 of l from this, by the M 
 
 ibstituting this value ol • ■' in 1 f), and 
 
 33 
 
258 MINES. 
 
 ■),=,,. its corresponding value for this of <■' : there obtains 
 
 •^=-^-, which result, substituted in the same Eq. (Jf) it then 
 
 'becomes </=c [l— *(1— ft)] 3 ; hence </=c ('"" 7 M )\ which is 
 
 the formula for undercharged mines. • 
 
 737...(t.\i.i.i kv Fkamks. Temporary galleries arc made of 
 framework covered in by plank, and are prepared but a short 
 period before they are required for pise, 
 
 738.. .Tin' frames of temporary galleries consist of four 
 pieces: two uprights termed stanchions, and two horizontal 
 pieces, the one at top termed a hap *///. and the bottom piece 
 a ground sill} PI. 8, Fig. A, shows the connection between 
 the parts of the frame. 
 
 The plank or boards which cover, in the frames are termed 
 s fleeting. The top sheeting of the frames usually consists of 
 boards from 3 feet 6 inches to 4 feet in length, from 7 to 12 
 inches in width, and from 1 to 1-| inches thick. The side 
 sheeting may have the same length and breadth, but need not 
 be thicker than from £ to 1 inch. To set the frames up and 
 retain them in their places, slips of plank termed battens are 
 used, which are about 2£ inches wide and 1 inch thick. 
 
 The frames may be either of well seasoned oak or pine, the 
 latter is preferable as lightest. The parts of each frame re- 
 ceive the dimensions in the annexed table: 
 
 Common gallery, 
 
 iu Bin u y^T j, sin 
 
 6X4, 
 
 5X- r ), 
 
 6X6. 
 
 Half gallery, 
 
 ■n_xH, 
 
 " 4*XU, 
 
 &X4*. 
 
 Branches, 
 
 3$X3, 
 
 " 34X3*. 
 
 ' HXH, 
 
 Small branches, 
 
 8X8, 
 
 3X3. 
 
 4 X 3, 
 
 739. ..Sua i r Frames* PI. 8, Figs. 3, 4, 5. A shaft is a ver- 
 tical pit, lined with sheeting on the outside of frames which 
 are placed horizontally, and at suitable intervals apart. 
 
 The cross sections of shafts are either squares or rectangles; 
 the dimensions of the sides of the section depending on the 
 object of the shaft. When this is for driving a gallery from 
 the bottom of the shaft, the dimensions of the shaft frames, in 
 
MINI B. 259 
 
 the clear, must be at least equal to that of the gallery, from 
 out to out of its sheeting. A shaft, sunk for establishing a 
 mine chamber simply, should usually he of the least dimen- 
 sions, which, to allow the miner to work with facility, must 
 not he less than 8 feel 1>\ - feet in the clear. 
 
 Two kinds of frames are usually requisite in sinking shafts: 
 a tojifrniin, Fig. 1, formed of four pieces, halved to fit each 
 other, which, when put together, have the same dimensions in 
 the clear as the shaft, each piece projecting beyond the side, 
 or having an over length of 1£ to 2 feet; the other is termed 
 a sid<? frani<\ Fig. 2, and, also, consists of four pieces of smaller 
 scantling than the top frame, halved at the ends to lit, its di- 
 mensions in the clear being the same as the other. 
 
 In very loose soil it may he necessary to use a temporary 
 frame. <<. Fig. 1. termed an auailiary fram\e. This is some- 
 what Larger in the clear than the preceding. Its uses will he 
 explained farther on. 
 
 The opposite pieces of each frame arc marked with a saw 
 out, termed a More, at their middle, on the upper side. The 
 scores serve to fix the position which the frame should occupy 
 when laid. 
 
 The scantling for top frames is usually 6 inches square; that 
 de and auxiliary frames 4.^ inches, for a shaft over A\ 
 in the clear. For smaller shaft.-, the scantling may he of 
 smaller dimensions. 
 
 740.. .Shaft Inn kval. The term interval, hoth in shafts 
 and galleries, expresses the distance between two adja 
 
 frames added to the thickness of the scantling of tie 
 measured in the direction of the axis of the shaft. ■ tc. With 
 tling and sheeting of the usual dimensions, the interval 
 should not he greater than '.)$ I 
 
 Pbob., Fig. 3. Tht depth qf a shafts and ih> height ■ 
 gallery 1<> lead from tlu bottom of tfu shaft, being* 
 
 d. 
 A «i'l tog I lier the In top 
 
 of it- ground sill, tiie thickness of tie 
 
260 MINES. 
 
 thickness <>f the shaft frame; t<> this sum add 2 inches for free 
 space between the gallery frame and the shaft frame next 
 above it, t<» introduce the top Bheeting. Subtract this sum 
 from the depth of the shaft, and divide the remainder into 
 any convenient number of equal or unequal intervals, each 
 not greater than 8| feet. 
 
 Lei the depth of the shaft, for example, be 22 feet, and the 
 height of the gallery -!'<;". Then: 
 
 From ground sill to exterior of top sill t 4M1" 
 
 Top sheeting 0.1 
 
 Shaft frame 0.4* 
 
 Free space D.2 
 
 Total 5.6* 
 
 This taken from 22 feet leaves 1G'.5£", which can be divided 
 into four intervals of 3'.4" each, leaving cue interval of 3'. 14/', 
 which may be placed either at top or bottom, but best in the 
 latter position. 
 
 '^...Construction of Shut. To construct the foregoing 
 shaft in a loose soil, there will be required a top frame; live 
 side frames for Hie intervals above estimated ; two for the re* 
 maining lower portion of the Bhaft; one auxiliary frame; four 
 battens for each interval of the length of the interval added to 
 the thickness of the shaft frame; from 12 to 20 Bquare pickets 
 about 18" long ; with the machinery and mining tools requisite 
 for the operation. 
 
 71-.. .The work is laid out by driving a pickel to mark the 
 axis of the Bhaft, and two others, which with the first are in 
 the vertical plane containing the axis of the gallery. A level 
 bed is then made for the top frame, the pieces of which are 
 accurately laid and confined by pickets, one at the end of each 
 piece; care being had to drive the two pickets of each piece 
 together, so ihat its true position may be kept, other pick 
 may be driven temporarily on the outside of the frame, a1 the 
 angular points' After the frame is laid, the accuracy of its 
 position is tested by seeing whether the distances from the 
 
MP- L'l'.l 
 
 centre of the central picket to the interior angular- points, "f, 
 in other words) the semi-diagonals^ are equal : if they are, the 
 position is correct. 
 
 M8... The excavation is now commenced, and, if the crumb- 
 1 i 1 1 ir of the soil does not interfere, may be carried as far as the 
 position of the first side frame; the sheeting boards, inserted 
 between the soil and the exterior of the top frame, being 
 gradually advanced with the excavation ; here the first side 
 frame is hung by four battens, two being nailed to each j 
 of the opposite Bides >>( the top frame and to the two com s- 
 ponding pieces of the side frame, the halvings of which are 
 turned upward : after these pieces are adjusted by their score! 
 and fixed, the other two pieces are laid on them, the halvings 
 down, and secured by nails. 
 
 71 I. ..This frame being fixed, the ends of the Bh( eting of the 
 
 next interval may be inserted between it and the sheetil 
 the tir.-t interval, and the excavation continued. The soil qow 
 becoaung troubli some by it> crumbling, measures must he 
 taken to retain it firmly until the second frame i> laid. 
 this purpose the auxiliary frame. Fig. 1. is introduced, ami 
 hung midway in the interval, like the usual frame.-. The 
 ■ ting which thus far ha- been gradually advtmced with the 
 ivation, inclined outward at bottom, to gain room 
 
 for the auxiliary frame, by wedges inserted between the boards 
 
 the two intervals. After the auxiliary frame is fixed, the 
 ivation and sh« i carried on to the bottom ol 
 
 interval, the next frame hung, and the 'sheeting for the 
 « interval introduced. The auxiliary fram< and 
 
 placed in the mxt position, when r< ached by th< 
 work will proceed in this order until the - 
 ted; wh< iven in the bottom, I 
 
 mark the central point. 
 
 i;k. A sketch, made to a suita 1 
 hand for in 
 
 more particularly m-ce^ary for trull cry w 
 for which diould b< 
 
numbered, as they serve not only for reference to guide tho 
 miner, hut to determine positions and dimensions <»t' some of 
 the important portions. 
 
 745... Combinations of Timber Q lllebibs. A gallery which 
 leads from another is termed a return, and is called obltqtn <>r 
 
 Idngular, according to whether the projections of the axes; 
 of the two galleries make a right or an acuU angle. The gal- 
 lery from which the return is made is termed a gallery of de- 
 parture. When the floor of the return rises or falls from that 
 of the departure, the return gallery is termed ascending or 
 d* 8d nding. 
 
 7 1»''...VTmi:ki.\<, Plans. To make a working sketch of a 
 combination of galleries, the projections of the axes are first 
 laid out; their points of intersection marked; and the dis- 
 tances and reference between all the points written. The half 
 width of each gallery in the clear being next set off on each 
 side of its axis, a line is drawn for it, then one parallel and 
 exterior to it at the thickness of the gallery frame, and, finally, 
 a second to mark the exterior line of the sheeting. 
 
 The line I), Figs. G, 7, 8, is the axis of the gallery of 
 departure, and .1 I> that of the return. The line a b is the 
 interior line of the gallery frames; o d the exterior line of the 
 same ; e f that of the sheeting. The corresponding Lines for 
 the remaining half of the gallery of departure, and those of 
 the return, will he readily recognized. The frames in and ///' 
 bound the entrances to the returns; and those, //,>', of the 
 auxiliary return, the entrance to the oblique return, Fig. 8. 
 
 The ease of a change of direction in a gallery is shown in 
 Fig. '•'• Here, to obtain room for the miner to handle the 
 sheeting, etc.. an end of an auxiliary gallery is made oil', on 
 the salient angle of the break, just large enough for the object 
 in view. Having set off these lines, the points of intersection 
 of the exterior lines of the sheeting of the return v\ilh the 
 exterior ami interior lines oC the frame of the gallery of de- 
 
 parture, are marked as follows, to determine the distance to 
 
 be left between the. two frames of the gallery of departure, 
 
MIXER. 263 
 
 between which the entrance to the return is placed: 1st. when 
 the projections oi the axes make a right angle, then the inter- 
 sections of the exterior lines of the sheeting with the Interior 
 lines of the framed are marked : the entrance to the return 
 will lie equal to the distance between the exterior lines of the 
 sheeting of the return : 2d, when the angle ie between 45° 
 and 90°, the intersection, 0, of the exterior line of the sh 
 ing of the return, which lies within the angle formed by the 
 axes, with the exterior line, c d, of the gallery frames, and 
 that, o', of the other exterior line of the sheeting with the 
 interior line of the same frames being marked, will give the 
 
 points between which the frames of the gallery of departure 
 must he placed to form the entrance; 3d, when the angle be- 
 tween the a --than 4."> : , the frame.- bounding the en- 
 trance to the return would fall too far asunder. It will, there- 
 fore, he requisite to make a rectangular auxiliary return from 
 the gallery of departure, into which the oblique return will 
 have it> entrance. To determine the position of the rectangu- 
 lar return. Fig. 8, a line, r », is first drawn exterior to the 
 sheeting of the gallery of departure, and at a distance from it 
 equal to the thickness of the frames to he aged for the aux- 
 iliary return; the intersection, », of the exterior line of the 
 ting, which lies within the angle of the axes and the last 
 line drawn, being marked, will give the point through which 
 the inner line of the frame- of the auxiliary return i.- to ]„. 
 drawn. This line being determined, all the other line- for 
 this return can he readily Bet out.' The re.-t of the problem 
 will he treated as in the second CI 
 
 V 17 . J^i v \i i -. From an examination of the ab< 
 it will be seen that tl t to be accomplished is so to] 
 
 the two frame- .,(' the gallery of departure, which bound 
 
 entrance to the return, that the itanchii 
 
 11 not he in the w ay of the miner wl • 
 
 ; or, in other words, if the petui . boi 
 
 that could he pn 1, like a dra 
 
264 min 
 
 of its axi>. tlic stanchions in question should not hinder this 
 movement. 
 
 reral other problems, of a like character, may present 
 themselves in returns, and in changes of direction in galleries, 
 which it will be unnecessary to treat here, a> the illustrations 
 above given will readily suggest the methods to be adopted 
 for their solution. 
 
 T48...1 >i i i:i:mi\ \ti..\ of < S \u.i i:v A kes. Saving set off all 
 the lines on the working sketch, and marked the positions of 
 the different frames, etc., at the junctions of the galleries, their 
 forms, dimensions, and also their .exact positions with respect 
 to any diced point, can be accurately determined from the 
 scale of the sketch, and be written upon it for reference in 
 conducting the work. . For example: in Fig. 7, the determi- 
 nation of the points o and o', fix the positions of the gallery 
 frames /// and ///, and the form, position and dimensions ot 
 the oblique frame q, of the return, where the galleries join. 
 Having set off these parts, the point /, on the axis of the gallery 
 of departure, equidistant from the points k and /, ot' the frame 
 y. can be determined. .This point, marked by a picket, serves 
 to fix these points, and, with the picket at F, the direction of 
 J B. 
 
 749... Landings. The portion of the floor of the gallery be- 
 tween the frames that bound the entrance to a return, is 
 termed a landing, as, for example, the spaces between the 
 frames m, m', and u\ v. The landing is in all cases horizontal, 
 as well as that portion of an oblique return between the oblique 
 frame y, and the one, a?, n « ■ x t succeeding, which last should 
 not be placed farther than an ordinary interval from the farth- 
 est point of y. 
 
 7:.M...(iAi.i.i i;v Ivii i:\ai.s. Having determined, by means 
 of the working sketch, the landings and their frames with 
 respect to the points of intersection of the axis of the gallery 
 of departure with those of the returns, the intervals of this 
 gallery can be calculated, and their positions marked out on 
 
iron z65 
 
 the sketch. The manner of making this estimate will be I 
 illustrated by the following example: 
 
 Let .1 B—118 feet, Fig. 1". be the total length of a galleay 
 of departure, estimated horizontally along its axis, from tne 
 central picket of the shaft from which the gallery starts. At 
 the point 6", 44 feet from A, the axis of a rectangular return 
 commences, and at I), 44 feet farther, that of an oblique one. 
 The part A C of the gallery, Fig. 11, is to l»e a common great 
 gallery; the part C D, Fig. 12, a common gallery; and the 
 part /> />'. Fig. 13, a great branch. With these data, it is re- 
 quired to determine the intervals for the different portions of 
 the gallery. 
 
 To find the interval for the first portion, A C, subtract from 
 the total distance, 41 feet, tin- following aggregate: 
 
 Half the width of the shaft in the clear 2'.2" 
 
 The thick ne-- ,.(' 1 lie In west shaft frame <». l.V 
 
 Half the width of the landing at C 8.6f 
 
 The thickness "fa gallery frame at the landing 0.5 
 
 5'.0" 
 which leaves -'- 1 feet to he divided into Bnitable intervals, 
 which may he done by making twelve of them each .". f. 
 inch 
 
 The intervals of the portion C I>. will he found as follow.-,: 
 From 44 feet take the following sum: 
 
 half the width of the landing at (' l>'ji$" 
 
 Thickness of the landing frame 0.5 
 
 The distance from I> (as found from the 
 
 landing frame beyond 0.9 
 
 Thickness of gallery frame at landing If 
 
 which leaves 10 fe< I 5 in< 1 i -. T ij can he divid nine 
 
 intervals, i ach 8'. l . and fonr sen. 
 
 ml the intervals for I ' • 
 
 fellowing ite: 
 
266 mhi 
 
 Distance from /> to frame of landing beyond it 4'.5" 
 
 Thickness of landing frame beyond 1) 
 
 Thickness of Last frame at li Q .-.I 
 
 This leaves 25 feet, which can be divided into six intervals of 
 :;'.!'" each, and two of 3'. 
 
 751...Slope-Block. In Betting the ground sills of frames in 
 ascending <>r descending galleries, a small cubical block <>( 
 wood, termed a slope-block, is nsed. This is a cubical block, 
 the edge of which is equal to the difference of level between 
 the ground sills of an interval. To determine the height of 
 the slope-block for any portion of a gallery where the intervals 
 are equal, or nearly so, the difference of level or of refer* 
 of the two extremities of the portion must be divided by the 
 number of intervals. Thus, in the portion of the gallery from 
 A to 6', Fig. 10, there is an ascent of 5', or 60", and twelve 
 intervals; the edge of the slope-block will, therefore, he 60- 
 lii" = r/. In the portion from C to J>. there is a fall of ■!'. 1". 
 or 40", and thirteen nearly equal intervals; the edge of the 
 slope-block will, therefore, be 3". 7, nearly. 
 
 752. ..Ai \ii.iAi:v Frames. In loose soils, besides the ordi- 
 nary gallery frames, there is required, as for shafts in the 
 same soil-, an auxiliary gallery frame. This frame, Fig. 14, 0, 
 Fig. 15, is somewhat wider than an ordinary gallery frame, 
 and somewhat lower than it. Its cap sill is rounded on top, 
 and has two mortices on its lower side, to receive the tenons 
 with which the two stanchions are finished. The mortices are 
 a little longer than the tenons — the latter being confined in 
 them by wedges when the frame is set up. To adjust the 
 frame when set up, a pair of folding wedges are placed under 
 each end of its ground sill. By these various contrivances, 
 the frame can he readily set up or taken apart. 
 
 753...CoNsTi:rcno.N of ( Jai.i.i- ,i:ii:s. To explain, now, the 
 practical operations in driving a gallery, let an example be 
 taken where the soil is loose, and the floor of the gallery rises 
 
min 2G7 
 
 from the point of departure. In this case, the first frame of 
 the gallery 0, Fig. 16, must be set up within the shaft and 
 against the shaft frames, <>n the side from which the gallery is 
 to open. The ground sill of this frame being laid, the stan- 
 chions are secured to the intermediate shafi frames of the last 
 interval by battens, and the top sill fastened. A horizontal 
 beam, <\ is then secured to the under side of the top shaft 
 frame of the same interval, to preserve the proper slope for 
 the top Bheeting when inserted, wedges being placed between 
 this beam and the sheeting hoard for this object. A like 
 arrangement for the side sheeting may be made it' necessary. 
 The excavation of the gallery is now commenced at top, by 
 forcing down with a crowbar the sheeting of the shaft, on the 
 side of the gallery. The earth i> removed gradually forward 
 and downward, and the gallery sheeting advanced at the same 
 rate. When the excavation has reached as low as the inter- 
 mediate bIi aft frame, the piece of it that sustains the lower 
 portion of the sheeting i> removed, to allow the excavation to 
 proceed. When, in this way. the earth is removed as far as 
 the middle of the first interval, the auxiliary gallery frame, 
 • 11].. to support the top and side sheeting until 
 the second gallery frame is placed. To place this last frame, 
 the position of the ground sill i.- first determined. Fig. 17, by 
 placing the slope-block, 0, on the ground sill first laid, ami 
 then, by a common masoi '. .1, upon the side of wtiich 
 
 the interval i> marked, laid upon the slope-block, bringing the 
 top of the ground >ill on the same level as that <>!' t. 
 block. The sill l>cim_ r adjusted and firmly .- mu- 
 
 cinous are next set up, a:. I by battens to the stanch 
 
 of the first frame, and th 
 
 The adjustments of the Btanchio are made hy 
 
 an ordinary plumb-line, by 1 which 1 
 
 ■ 
 and ground sills brou^ ical plai 
 
 the gallery. 
 The battel illy. In a 
 
2G8 MiN 
 
 are nailed, alternately, at 4 and v inches below tbe cap >\\\. 
 In others, Fig. L7, they are nailed I incbes below Ihe lowe* 
 of the cap sills of the two frames which they unite; this will 
 bring them at 4 inches, added to the height of the slope-block, 
 below the ot"her. 
 
 The auxiliary frame is not taken down until wedges have 
 beeil placed between the sheeting and the frame last placed, 
 in order to introduce the boards for the next interval ; and 
 these last are kept in the proper direction, as the excavation 
 is advanced, by wedges inserted between them and the sheet- 
 ing of the interval finished. 
 
 754...Bkan( n (i.M.i.i i;n:> a i. a I loi.i wpaisk. These galleries 
 are of tin- same dimensions as small branches; the frames are 
 made of plank; they arc placed touching each other, arid 
 serve at the same time both as frames and sheeting. 
 
 Each frame consists of four pieces; the stanchions have a 
 tenon at each end, Fig. 18, fitting into notches cut in the cap 
 sill and ground sill to receive them. 
 
 When the gallery is an ascending or descending one, the 
 ends of the staiichions arc cut obliquely, in order that their 
 sides may always be vertical. 
 
 Fig. 1!' is a plan and section of this description of gallery. 
 
 755. ..For the purpose of limiting the effect of explosion of 
 mines upon the branches leading to them, and. at the same 
 time, to enable the miner, acting on the defence, to push for- 
 ward and open a new branch toward the crater, a portion of & 
 branch leading toward the mine is math' of heavy frames of 
 the foregoing construction. The timber recommended for the 
 purpose is oak. and the pieces of each frame are \"2" wide and 
 I" thick. The portion of this strong framework, at the ex- 
 tremity, is solidly filled in with pieces of 4" scantling, from G 
 to LO feet iii length. For a branch 28" high and 24" wide, 
 m'ycii horizontal layers will be required, each layer consisting 
 of 5 pieces. The centre piece of each layer may have a rope 
 handle at its end to allow of its being drawn out readily. 
 Filled in this way, and having earth well packed between the 
 
mini-. 269 
 
 pieces, branches of this description will not be damaged by 
 the explosion of mines of from 6 to 10 feel line of leasl r< 
 ance, even when the mines are within 41 to 6 feet of the 
 branch. From their cHief object, these branches arc termed 
 by the French rameaux de combat. 
 
 756.. .Shafts a i.\ Boule. These shafts arc lined with fram 
 made of plank, connected togethei as shown in Fig. 20. 
 
 In Fig. 21, a section of a shaft a la Boule is shown, which 
 is sufficiently explanatory to render any other description 
 unnecessary. 
 
 This kind of shaft can only be used with advantage in favor- 
 able >"il. <>n account of the difficulty of introducing the frames 
 sufficiently near each other; they are commonly placed one 
 foot apart, as shown in the figure. Large gabions, 6 feet long, 
 and from .'! feel <i inches to 4 tcct in diameter, arc sometimes 
 used tor Lining shafts near the surface, smaller gabions being 
 introduced as the work is proceeded with. 
 
 757.. .For the purposes of quickly establishing small camott- 
 flete and fougasses, a boring apparatus has been resorted t.-, 
 the diameter of the boring tool being 4". This machine 
 worked like ordinary tools of litis kind. It i.- charged for 
 
 ion by inserting powder in cylindrical cartridges of some- 
 what less diameter than the shaft, which are well rammed for- 
 ward; or, if a large charge i- requisite, the end of the shaft 
 can he enlarged by a tool with a joint, which will admit the 
 
 gradually to 
 at tin- end. made in this way are tern 
 
 shafts or branch* 
 
 758. I i i.i ( i io\ 
 floor of the gall< ry i.~ not more than 10 or 12 feet below 
 surface, it will b< c-h for ti 
 
 The width of the I at the I fl he the 
 
 the gallery from out to out If tic soil is ven H 
 
 i !y ].. r; 
 
 above tin »uld 
 
 be left, and . and r><» • 
 
 
270 mini.-. 
 
 additional depth of 6 feet. These berms serve the place of 
 scaffoldings, to pitch tlie earth out. 
 
 If the soil is very loose, the slopes will require to be bus* 
 tained by a sheeting to prevent the earth from caving in. 
 After the masonry is completed, the excavated earth is care- 
 fully replaced. 
 
 V.V.i... When the construction is made entirely under ground, 
 a wooden gallery is first formed, the width of which, between 
 the frames, in the clear. Fig. 22, is equal to the width between 
 the piers of the permanent gallery from out to out; its height 
 being such that there will he (! inches between the crown of 
 the arch on the exterior and the cap sills. The top and side 
 sheeting should lap about 8 inches. 
 
 When the gallery is completed, a new set of ground sills are 
 laid alongside of those of the gallery, their length being equal 
 to the width of the permanent gallery in the clear, Fig. 23. 
 A new set of stanchions, o, o, are set up on these sills, to sup- 
 port a new set of cap sills of the same length as those of the 
 gallery. Vertical hoards, a, are placed alongside of stanchions 
 of tin- wooden gallery, and are buttressed against the sheeting 
 by two horizontal pieces of scantling, c, <?, one near the top, 
 the other near the bottom of the gallery. "When this new 
 arrangement is completed, the frames of the gallery first set 
 up can be taken down, and the masonry commenced. 
 
 The foundations of the piers, Fig. 24, are laid with an interior 
 l of (i inches. The piers are then carried up, the lower 
 horizontal buttress being gradually shifted up so as not to 
 interfere with the work, and the lower courses of the side 
 sheeting, which have now become unnecessary, being removed. 
 AVhen the piers are completed, the stanchions are taken down 
 and replaced by pfops, j>, _£>, resting on the outside of the tops 
 of the piers. 
 
 When this change has been made, the way is clear for turn- 
 ing the arch. For this, four common centres, A, A, Figs. 25) 
 26, made of boards, will be requisite. Each of these centres 
 is 18 inches broad, and is secured to a rectangular frame, o, of 
 
MINKS. 271 
 
 small scantling of the Bame breadth, and as long as the span 
 of the arcli. Each centre thus prepared rests upon a trestle, 
 q, y, of sufficient height to bring the centre in its trne position 
 to receive the masonry. 
 
 The masons, to expedite the work, commence at the middle 
 point of the gallery, where two of these centres are placed to- 
 gether, and close the arch over them; the other two centres 
 are then placed alongside of these, and the arch in like man- 
 ner is elosed over them; the two first are then taken down, 
 and removed to the outside of the two last Bet up, and the 
 arch is thus carried on toward the two ends. The wood 
 work of the gallery is taken down as fast as the masonry sup- 
 plies its place. 
 
 7»'»"...In the main galleries of communication, arched rec 
 are formed to servo as depdts, etc., for the implements of the 
 miners. These recesses are from 6 to 1- feet in depth and 
 usually of the same width, and may be placed at interval- of 
 15 or l' 1 * feet from each other. Similar dispositions are made 
 in the listening galleries for the magazines of earth required 
 for tamping the mines ; small portions of galleries, from 6 to 
 12 feet in length, are run out at right angles to the listening 
 gallery for this purpose. A sufficient number of openii 
 mn>t al.~o be left in the piers of the listening galleries, for the 
 construction o! the branches leading to the mine chambers. 
 
 761. ..In I- . and to give greater r irv 
 
 galleries to glob< 
 
 them a cross section, of an oval form, instead of th 
 given. Galleries of this form would be of more difficult i 
 strnetion and cost more than those of the usual form. 
 
 T62...When Bevera] galleries branch off from t 1 point, 
 
 a large arched chambi r oi a sqn; >nal fori 
 
 tructed, which s ind is also arrai 
 
 with a crenated wall within it to defend the rm 
 galleries. In PI. A. cample, if tl 
 
 //, </, meet at a p irched cham 
 
 to com;- i, and within t: 
 
272 mines. 
 
 thin wall, constructed with loop-holes to fire in the direction 
 of tin- most advanced galleries, <',a,a. 
 
 763...The piers of the galleries are also arranged either with 
 grooves or offsets, so that harrier- may be mad.' within them 
 for defence against the enemy's miner when he penetrates 
 into tlic gallery. In some cases a simple pit is dug across the 
 gallery and covered by boards, which are taken up when the 
 communication is required to be cut off. 
 
 764.. .Mini: Chambers. The chamber of a mine is a cavity, 
 A, formed to receive the charge of powder. Fig. L'T. 
 
 When the chamber is made at the end of a gallery, the cen- 
 tre of the chamher is placed on a level with the floor of the 
 gallery. It is usually better to place the chamber at the end 
 of a small branch return on one side. When the charge is 
 not to be exploded immediately, or the ground is much satu- 
 rated with moisture, it should be placed in a well pitched 
 wooden case, or a good cask, or in a wooden case covered with 
 tarpaulin, or any like expedient adopted that may he at hand — 
 the best receptacle is a water-tight tin case. 
 
 In dry ground, and when the charge is to be soon exploded, 
 canvass hags will answer. 
 
 If the case to contain the powder is not more than 2 feet 
 square, it may he introduced into the chamher ready made ; 
 if of a greater dimension, it must he put together in the cham- 
 her, the pieces to form the sides being arranged like the frames 
 ot branches a la ]I.<>Ihin<I<t.ix<\ 
 
 An ppening is left at the edge of the cover, about 4 inches 
 square, for the introduction of the charge, and a similar one 
 in the side to receive the hose-trough. 
 
 The edge of a cubical case to contain a given charge is cal- 
 culated on the supposition that 58.5626 pounds of powder are 
 equal in hulk to a cubic foot; and l,(»oo cubic inches will, 
 therefore, contain 33.89 pounds. From this, if J' represent! 
 the given number of pounds of powder, and X the side of the 
 cubic sought in inches, then 
 
mini b. - 273 
 
 33.80 : (io) 8 ::P: .r 3 , 
 
 X=3.W{- /'. 
 That is, to obtain the edge of the cubical case in inches, ex- 
 tract the cube root of the given number of pounds of powder 
 and multiply it by 8.09, or 3 L-10, nearly; 
 
 From the bursting of guns, where the wad has not been 
 pressed down on the powder, it has been thought that in 
 charging mines a like increase of effect would be produced, 
 by leaving a certain free spacearound the case. Experiments 
 on this point have not been sufficiently decisive to lead to the 
 adoption of this in practice. 
 
 765... Hose TrouoHs. The hose trough is a small wooden 
 channel, in which is placed a linen bag tilled with powder, 
 and termed the powder-hoee, to tire the charge. 
 
 The bag should be of close texture and well sewed. 
 
 These troughs are made L£ inch square in the clear. Tlic 
 four pieces of which they are composed; the sill, sides and 
 top. or cover, are from J to h inch each in thickn* 
 
 A trough should penetrate the powder case about 1 incl 
 and should exactly tit the opening left for it. 
 
 It i.- fasti rti d to the floor of the branch by nails, through 
 the -ill, which enter small pickets driven to receive them. 
 Sora< times the eidi - of the trough arc confined by picket 
 prevent its being disturbed. 
 
 The different lengths of the trough should be cut to tit ex- 
 actly. Each portion of the trough should have its cover well 
 fitted and secured with one peg only, in order that it may 
 moved to introduce the powder-hi 
 
 The trough i- said to make an elbow when it 
 direction. The pi< c< e forming an elbow should be firmlj 
 simply connected; I "•', show the mo I 
 
 of cIIm.v 
 
 766. ..Proportioning Trains. When several mines are to 
 be tired at i • moment, it rtion 
 
 r trains that, starting from tl 
 
274 min 
 
 time from that point to the charges may be all equal. The 
 following cases Bhow the manner of obtaining this result: 
 
 For two charges, Fig 30, place a trough on the shortest line 
 from the one to the other, mark the centre of it, and lei the 
 principal trough join it in that point* 
 
 For three charges, Fig. 31, connect, as above, the two which 
 are nearest. Let a trough from the middle point of this to the 
 third ehargej biseel tin- whole length of trough between this 
 third charge and either of the others; then let the principal 
 trough be joined to this last point. 
 
 For four charges, Fig. 32, first connect them two and two, 
 then join the central point.- and proceed as above. 
 
 The elbows of a trough impede the communication of the 
 fire, for which an allowance must 1k> made when proportioning 
 the trains, each elbow being valued at 3 inches; thus, it' on 
 one side of the point where the principal trough connects is 
 one elhow more than on the other, the principal trough should 
 he placed :; inches nearer to the charge on that side, which is 
 done by placing it 14- inches from the central point toward 
 that side. Square elbows impede somewhat more than oblique 
 ones. 
 
 Experience has Bhown that two powder-hoses may be placed 
 
 within is inches of one another if covered with earth, and ex- 
 ploded separately without interference. 
 
 707... Tamping. Mines are tamped either with earth and 
 sods, with earth and wood, or with sand-bags. 
 
 To tain]) a branch with sods and earth, the miner first tills 
 the branch with sods lor a length of 3 feet, commencing at the 
 ehamber. The sods are piled in regular layers, the precau- 
 tion being taken to throw loose earth over each layer, to fill 
 the voids between the sods. When this length is finished, the 
 miner lills in for an additional '■'> feet with earth, which should 
 he well packed. Another Ipngth of sods is laid of 3 feet, and 
 so alternately through the entire branch. 
 
 To tamp with wood and earth, a stout shield of thick hoards 
 is first placed across the branch and firmly buttressed against 
 
 
M!\ 275 
 
 the chamber, the branch is then filled with well packed earth, 
 resting against the shield for a length of •"> feet; billets of 
 round <u- square timber are then packed across the branch for 
 a Ldngth, likewise, of 8 feet ; another length of earth of the 
 same thickness is packed in against the Wood, and bo oil for 
 the entire length to be tamped; finally, at the end of the 
 tamping another shield is set up and firmly buttressed. 
 
 Sand-bags, for tamping, are of the ordinary dimensions. To 
 tamp with them, a shield is first placed against the chamber 
 and well buttressed. The branch is then filled up with sand- 
 bags laid in regular Layers, loose earth being thrown over each 
 layer to close the joints. This U the best kind of tamping, 
 it can be removed most s] lily after the explosion. 
 
 The length of tamping is regulated by the line of least re- 
 nee of the mine; the part <>f the branch tamped equal to 
 twice this line. This length must he measured in a right line 
 from the chainher to the point of the branch where the tanip- 
 ing terminates, and not along the windings or elbows of the 
 branch. 
 
 768. ..As tamping is a laborious operation, and requires con- 
 rable time to do it thoroughly, it has been proposed to 
 insert a trough of 4" or 5" section, in tin- branch or -haft lead- 
 ing from the mine chamber to the main gallery, or branch, 
 and then to tamp in the usual manner around the trough. 
 Prepared in this way, the charge made into cylindrical car- 
 ta powd< \ >■ portions in a 
 cylindrical vessel, attached by a joint at it.- bottom to tin 
 of a rod, can bi I through the trough and be 
 thrown into the chamber in a very short time, and I 
 he immediately afterward explo I 
 
 769.. .Id ethoi common methods 
 
 firing mil by tin \k and the ; 
 
 i two method 
 
 The monk i> a bit 
 to he tired by it 
 
 
276 mines. 
 
 * 
 
 sprinkle some dry, fine powder on it: cover this powder < 
 with another sheet of paper, secured at its four corners with 
 »lrv earth or stones; pass the monk through a hole in the 
 apper sheet, and Let it project half its length above it, its : 
 being plunged in tire powder on the bottom sheel ; set fire to 
 the monk at top with another piece of agaric, termed an in- 
 fm m< r, of the same dimensions and form as the first, and retire 
 quickly. 
 
 The bOXrfcrap, Fig. 33, is a box 18 inches high and n' inches 
 wide in the clear. The bottom consists o\' a piece of plank 
 18 by Id inches, and its cover is fixed at one side only with a 
 wooden pin, about which it can be turned. 
 
 At 6 inches from the top of the box a horizontal slit is made 
 in one of its sides, and grooves in the two adjacent to it. t<> 
 receive a piece of hoard, which ought to slide freely in this 
 arrangements. In the lower part of the box an opening is left 
 on the side opposite the one cut for the slide, to admit the 
 powder-hose. 
 
 To fire the train, place the box against the extremity of the 
 tamping and secure it well ; tie a string to the slide, and lead 
 it along the stanchions of the gallery on pegs driven for that 
 purpose ; put the end of the hose into the hex through the 
 hole left for it, and spread on the top of it some dry, tine pow- 
 der; then put in the slide and close with earth, or rags of sand- 
 hags, all communication between the lower part of the box 
 and the branch ; place a star-match of six or eight points, 
 
 Well lighted, on the Blide : replace the cover, then pull the 
 string and the star will fall below and fire the mine. 
 
 The two methods above described have the inconvenience 
 of requiring a powder-hose, which, from its own explosion, 
 poisons the galleries. They have also, and more particularly 
 the monk, the defect of not producing the explosion always at 
 the instant desired. 
 
 To avoid these inconveniences a galvanic current has of late 
 been applied to lire mines, and with complete success. This 
 
MP- L'77 
 
 method has been found particularly serviceable in firing 
 charges under water. 
 
 A small rocket, Fig. 34, with a hemispherical head of wood, 
 lias, also, been tried successfully. To use it. a wooden trough 
 with a smooth interior must be placed from the charge to the 
 point where the rocket is to start : tin tul>es have been recom- 
 mended, but are found not to answer. The rocket i- then 
 placed in the end of tin- trough, the quick-match with which 
 it i> provided is lighted, ami the rocket start.- with very L r re:it 
 velocity, penetrates the charge and fires it. 
 
 When the rocket lias to pass elbows, or when it is desired to 
 fire several mines at tlie same moment, q rocket is placed at 
 each turn of the trough, with it.- quick-match secured round a 
 nail ; the first rocket arriving at the point where the oth< i 
 placed fires it. In order the Letter to insure the first rocket 
 
 firing tl d. a quantity of powder (^ ounce) should lie 
 
 BtroWU about the match of the latter, protected by a wed 
 lhaped slip of deal, nailed to the bottom of the trough ; the 
 
 rocket meeting this | »ver the powder, which its rapid 
 
 motion would otherwise disperse. 
 
 A rocket may be made to turn in a circular trough, when 
 
 ■ 
 
 the radius of that part is not Less than twice the h ngth of the 
 rocket. 
 
 In order to prevent the Bmoke of the charge pcn< trating the 
 gallery through the trough, one ( ,r two small iron traps i 
 lie j. laced in the trough, which. . by the ro< 
 
 fall again by their own weight, and cut off all commui 
 between the gallery and the charg 
 
 A rocket 6 inches long will travel 100 yards, 
 it.- velocity : si that ts . ed at t 1 
 
 Brent, to run very different 
 interval in the times of their arrival. Th 
 
 proportion I 
 simultaneously, which with powd< 
 
 The ordinary rocket I 
 
 in d 2-5 of fit 
 
278 MI.N 
 
 and l-. r » of charcoal dust. These ingredients should be very 
 carefully mixed, to make the rocket burn uniformly. Its 
 Usual diameter is nearly f of an inch, and its entire weight 
 about H ounce. Rockets may be made much smaller when 
 required. 
 
 7T.0...The great advantages offered by galvanic batteries for 
 exploding mines at considerable distances from the battery, 
 either when isolated or combined in groups for simultaneous 
 effects, have led to experiments which, from the uniform cer- 
 tainty of the results, besides other obvious advantages over 
 any of the other methods above given, will, probably, cause 
 the genera] adoption of this apparatus for military min 
 
 The method mostly adopted by the Continental engineers is 
 tlu' combination of Bunsen's battery with Ruhmkorf's appa- 
 ratus for intensifying the current of induction. A copper 
 conducting wire, which is insulated by one or two coats of 
 gutta-percha, connects the charges with the galvanic appara- 
 tus, The charge is exploded by passing a .-park through a 
 very small portion of fulminate of mercury inserted between 
 the ends of two popper wires, which are enclosed within a 
 short tuhe of gutta-percha, coated within with sulphuret of 
 copper. The wires are bent near the end of the tube, ami 
 twisted around each other. A little meal powder is thrown 
 around the fulminate and the tuhe, which, with the tube and 
 the bent part of the wire, is tightly closed in a small gutta- 
 percha bag, t«> keep out moisture. To fire a single mine, one 
 end of the twist is soldered to the conducting wire and the 
 other inserted into the earth to complete the circle, for sev- 
 eral mines, to he exploded at the same time, Conducting wires 
 
 conned the mines, and tlu- ends of the twist are soldered one 
 to each conductor, except the end one, which has one of its 
 ends inserted into the earth. By this combination, the series 
 will be exploded without any sensible- ^difference of time be- 
 tween the nearest ami furthest mine. 
 
 771... Blasts. Blasts are small chambers, or holes made in 
 rock, or masonry, charged with powder. The forming of 
 
mi\ 279 
 
 blast-holes requires the uso of particular toots, called borers, 
 jumpers, scrapers, needles, and tarrvpirig-bwrs. 
 
 To form the blast-hole, two or three men arc required ; one 
 holds the borer with both hands, while the head of it is struck 
 with sledge-ham mere by one or two others. The first turns 
 the borer at each stroke so thai the hole may be circular, and 
 from time to time clears it out with the scraper. 
 
 When the hole required does not exceed [5 inches in depth, 
 it may be excavated in the above manner; but if 20 inch< - o# 
 more deej., the jumper is generally made use of. The miner 
 holds the jumper in both hands, raises it. and lets it fall in the 
 hole, turning it continually; he also clears the hole with the 
 scraper. When the Btone is of a very hard description, it is 
 usual to pour wat rionally into the jumper hole. 
 
 To load the hole, fill about one-fourth or one-third of it with 
 powder, according to the nature of the stone. The charge fof 
 a depth ol I s in ft "in 8 to 1 2 oun< 
 
 T<» tamp and prime the blast hole, the needle is first intro- 
 duced, plunging it well into the powder and placing it on the 
 smoothest side of the hole; then a layer of clay is laid on the 
 powder, and is closely pressed down with the tamping-bar. 
 
 ( Mher similar layers are then hod. or layers of brick redu< 
 to .-mall bits, the needle being turned repeatedly. It is at 
 to press down the first layers with a bar of wood— the b< 
 of a tool lor instance — and the latter ones with the iron tamp- 
 ing har. When the hole i.~ thus filled up, a small shell of - 
 is formed round the needle, which i> then withdrawn, the hole 
 left by it i.~ filled with fine powder, and it i> tired with a monk 
 or a 1 port-fire. 
 
 The use of the n< 1 die ; - often dispensed with, in which c 
 the priming i> rolled up in a brown paper, or ■ 
 
 traduced in straw thrust into one another. I prii 
 
 aced in the hole at th 
 may pent tratc wed into the !.,••. 1 . p., tan , 
 cuted a- before. 
 
 Tl; 
 
280 MINES. 
 
 also be dispensed with, the hole being filled over the charge 
 with wry fine dry sand, poured in witboul any pressure. 
 
 The many accidents that have happened in priming Masts 
 have led to the invention of priming-fuses, wh'.^h are mad 
 burn somewhat in the same way as the fuse in the small Chii 
 fire-cracker. Their use is far safer than any of the former 
 metli< 
 
 Fur blasts under water, the charge is inserted in a water- 
 tight tin ease, and fired either by a galvanic current or a prim- 
 ing-fuse, which is protected from the water by a small tube 
 connected with the charge, and leading to the surface of the 
 water. 
 
 The result of many experiments has shown that in blasting 
 rock a large portion of the powder — nearly halt — may he 
 saved, by mixing with the remaining part tine dry sawdusl <>f 
 elm or beech. In blasts exploded in this way, the effect is not 
 the same as when the full charge of powder is used ; the rock 
 splits into fewer and larger pieces, and, to finish dividing 
 them, a more frequent use of the sledge-hammer is required. 
 
 772...1 >i.moi.itions. Xhe charges of mines intended to over- 
 throw masonry, are calculated as in a common soil, by using 
 the proper quantities given in the preceding table for the dif- 
 ferent kinds of masonry to be destroyed. 
 
 773...To r.Ki.M 11 a Wall. First ascertain, if practicable^ 
 the thickness of the wall, and then proceed thus : 
 
 JFirfit case. When the wall is from 2 to 3 feet thick, place 
 one or two barrels of powder against the lower part of it, and 
 fire them. 
 
 Second case. When the wall is from 5 to G£ feet thick, place 
 One or two charges under its foundations, plumb with the 
 centre of the wall. 
 
 Third case. When the wall is from 9 to L2 feet thick, open 
 at the foot of it, or about L2" above the water level, a branch 
 
 gallery, which must be driven to the centre of the wall ; then 
 make two perpendicular returns to this branch, and place the 
 powder at their extremities] Fii^. 35. 
 
MINI ■>. 281 
 
 774. ..To Bbeagh a Wall with a Tikkaoe. Open at the 
 foot of the wall, or 1*2" above the level of the water, a branch 
 perpendicular to the direction of the revetement; drive it 
 through (lie wall to the earth, then make, to the righl aftd left, 
 two other branches, following the hack of the wall, and each 
 in length equal to its thickness; place the charges at the end 
 of these branches, so that the centre of each charge may be 
 flush with the hack of the wall. 
 
 ?76...Demolttion of Revetements. When the revetement 
 is withont counterforts, or the counterforts are not more than 
 3 feet thick, several branches are driven perpendicular to the 
 direction of the revetement, at equal distances apart. The 
 charges used should produce craters that will cross each other 
 a little. 
 
 When the wall baa counterforts of the usual dimensions, the 
 charges are placed, as far as practicable, in the lines of their 
 axes and their junction with the revetement, Fig. 36. 
 
 When time presses, instead of making one branch for each 
 pair of charges, one is made for each charge; and the whole of 
 the charges are placed at three-fourths of the thickness of the 
 wall, and so regulated that their craters may slightly run into 
 each other. Fig. 87. 
 
 When galleries cannot be driven at the proper level for the 
 charge, a- in the demolition of wharves, etc. shafts are sunk 
 behind the revetement, or at a Bhoii distance in the Pear of it, 
 big. :;**. and branch''- are then driven to the positions tor the 
 charges; or. which is still better, becanse it is a more sp< 
 operation, a shaft may be sunk for each cha 
 
 The depth of the shaft mntl be sufficient to admit ^ 
 proper length of tamping. 
 
 If. at the same time with the wall, a n arth in I 
 
 rear of it is to be destroyed,; prolong the branches in the in- 
 terior of the earth sufficiently t<> allow of the □ 
 back of the wall exploding before those placed in the earth 
 
 W • . ' • ;- a eralh of the r< 
 
 36 
 
282 mini-. 
 
 ment, the charges should be placed along this gallery, exca- 
 vating chambers fotf them in the revetement at distances apart 
 
 equal to twice their line of leas: resistance, viz.; at two lined 
 intervals. 
 
 The portions of the gallery in the rear of the charg* 
 then tamped; at each end, the length of the tamping should 
 be equal to twice the line of least resistance of the extreme 
 charges. 
 
 The following method has been employed with success. 
 Regarding as the tine of least resistance the distance from the 
 gallery to the surface of the wall, imagine a r«>w of common 
 mines placed at two lined intervals throughout the length and 
 calculate the sum of their charges, to which add one-half for a 
 great gallery ; place the whole charge in several heaps, with 
 strong trains leading from one to another. Then, tamp 
 strongly and carefully the ends ot the gallery, leaving the 
 space intended to be demolished void. When the galler 
 more than 2 yards wide and high, or if it have many ieSUea 
 difficult to tamp, the charge of powder must be farther aug- 
 mented to produce the desired effect. 
 
 TY6...Dbmouttob ok Towebs. If the interior diameter of 
 the tower be 6 yards or more Fig. 41, drive branches into a 
 wall from the interior of the tower, and place charges 80 as to 
 be a little nearer to the interior than to the exterior of the 
 wall. When the tower is connected with walls, charges must 
 Ik- placed at their points of junction. 
 
 When the tower is but 4 or 5 yards in diameter, Fig. Il\ 
 sink a shaft to about the level of the bottom of the foundations, 
 and place a charge there corresponding to the line of least 
 resistance, measured from the centre of the charge to the 
 foot of the wall outside. 
 
 Cover the floor of the tower with two rows of small beams, 
 then lay upon them two beams crossing and halved into one 
 another; and place upon these uprights abutting firmly against 
 the masonry of the arch. 
 
 When a shaft cannot be sunk on account of water, and when 
 
MINES. 283 
 
 the tower has loop-holes which prevent charges being plated 
 in the walls, lay the charge on the floor of the tower, enclosed 
 in a strongly constructed case, propped on all side* against 
 the masonry. 
 
 When the tower is square, and has several floor! or Btagee, 
 the charges may lie placed at the four corners of the ground 
 story, tamping the tir^t lloor. 
 
 777...I>KM<u.rnox OF PoWDEB Maoaxjxks. Place chars 
 the piers and ^able ends, so that their craters may slightly 
 cross each other. 
 
 When time presses, a charge is laid on the floor of the mag- 
 azine, the doors are barricaded, and it is tired with a hose led 
 outsiile. 
 
 To determine the quantity of powder required for the heap, 
 calculate the number of common mine.- required to overturn 
 a revetement of tin 1 same length and thiclcness as the walls 
 a magazine, including the piers; add pne-half the sum of the 
 charges tlm* found, and place the whole in one heap in the 
 centre of the magazine. 
 
 The above method is only applicable to magazines of not 
 more than 150 square yards surface. If of greater capacity, 
 the quantity first found should be increased 1-1" for every 15 
 Square yards of additional surface, and be placed in tw 
 more heaps, connected with powder-hose to tire them simul- 
 taneously. 
 
 77v..l M M"i iiion oj |',i ; ; _,., the piers 
 
 of which are from ! to J ' thick, place in one of the piers 
 two oharges oJ 130 to 160 pounds each, 1 
 plana to the bridge op which to place the powder-h 
 
 I: the pii r be from 6 to L0 fo< I thick, drive in the middle of 
 it, parallel to small: , at the ends of wb 
 
 place charges of from 200 1 i. 
 
 When there is not time to place charges in the interior of 
 the j the arch l - 
 
 ler. 
 
284 
 
 MINES. 
 
 This quantity of powder lias broken semicircular arches of 
 eel >]>an. and -1A feel thickness al the crown. 
 
 Another good method is t<» cul a trench in the form of a 
 cross. Fig. 1 1, over the middle ot' the arch, each branch being 
 about LO feet long, and carried down t<> the extrados. Place 
 in each branch 200 pounds of powder for an arch 3^ iect 
 thick, and cover the charges with timber, earth, etc. 
 
 An arch may also be blown up by suspending an open 
 trough nnder it with cord.-, and placing in it charges of pow- 
 der similar to those already stated fior trendies cut on the .sur- 
 face. 
 
 When tin' savin-- of powder is of consequence, sink a Bhaft 
 down to one of the haunches, Fig. 45, and place the powder 
 in- one mass, unless the bridge 1 be very wide. An arch of 18 
 inches or 2 feet thickness, of a bridge 20 feet wide, may thus 
 be destroyed with 45 pounds of powder, if a loading can be 
 applied over the charge, giving an equal resistance to the arch. 
 
 If the bridge is more than 20 feet wide, two shafts must be 
 sunk, and charged as before described. When the side walls 
 of the bridge above the piers are slightly built, and the load- 
 ing of the arch is of loose rubbish, a small gallery should be 
 driven about 5 or 6 feet from the arch stones, along the axis 
 of the pier, as at A\ Fig. 45; a return is then made toward 
 the arch, and the charge is placed in contact with the ex- 
 trados. Bridges of timber may be blown up by suspending 
 barrels of powder under one or several bays. 
 
 779... Demolition of Houses. Begin by undermining the 
 windows and doors, and cutting away the piers between them, 
 so as to leave the building supported by a * ew piers only, 
 nearly square. Place in each of the piers a charge of from 
 13 to 16 pounds of powder, tamping well with wood. Pro- 
 portion the trains to the different charges, so that they may 
 be simultaneously exploded. If pressed for time, resort to 
 the same methods as for towers and galleries. 
 
 To destroy palisades, or gates, doors, etc., the best method is 
 to suspend a leathern bag, filled with powder, either with a 
 
mini-. 285 
 
 forked stick, a strong gimblet, ot a stout copper nail, against 
 tlif gate or palisade. The bag should have about an inch of 
 port-fire tirmly secured in one side of it, to communicate the 
 lire to the charge. To throw down a strong palisade, from 30 
 to 50 pounds of powder should be used. To burst open a 
 town irate, 60 or 7" pounds of powder will be required^ 
 
 780..'.Fotf€U£SEB. Mines are so called when placed at the 
 bottom of small shafts, from 9 to 12 feet deep. The powder 
 is Lodged in one of the sides of the shaft, and it is fired from a 
 secure spot by means of a powder hose, brought up one side 
 of the shaft, and carried in a trough, parallel to the ground, ■> 
 or 6 feet below the surface. When there is no occasion to fear 
 that sheik may fall on the part where the trough is laid, it 
 will be sufficient to place it '2 or 2£ feet under the ground. 
 The powder case and trough should be well pitched, the shaft 
 tamped in the strongest manner, and the earth round about 
 the shaft be dug over, that nothing may indicate to the enemy 
 the position of the fougasse, 
 
 7^1. ..Sin i.i I"oi • Shells may be huricd singly, Of in 
 
 Bmall heaps, and be made to burst either under the ground or 
 on its surface. 
 
 If they are to burst under the earth, they must be sufficiently 
 charged to produce a crater, through which the pieces are pro- 
 jected. 
 
 Jt' they are to burst on the surface, the requisite quantity of 
 
 powder to produce a crater and throw out the shells must 
 
 lodged under them, while these latter need only have a suffi- 
 cient charge to burst them. 
 
 In all cases a box is at livided into two parts by 
 
 a partition. The shells are placed in the upper part, their 
 fuses project through the partition, and extend from £ to 1 inch 
 below it. 
 
 In the lower, part, the hose only is placed when the shells 
 are intended to produce their own crater; but | auffi- 
 
 I to produce th< 
 tended to burst on ti md. 
 
286 
 
 MINES. 
 
 Tin' effects produced by common and shell fougasses are 
 very Limited, and only destructive near their craters: con- 
 sequenjkly, they should not be exploded until the enemy is 
 above theui. 
 
 Dks< iui'tkin ok Shell. 
 
 ¥\ i.i. I.'iiai;i;k OF thk 
 Sn k i.i.. 
 
 IlMllI AT WHICH THK KILL 
 
 ( iiaki.k rkoin i'KS A 
 I'UATKK. 
 
 
 Lbs. 
 
 Oz. 
 
 
 
 Calibre, 5 J 
 
 1 
 
 
 
 2' 
 
 0" 
 
 8 
 
 2 
 
 9 
 
 2 
 
 10 
 
 " 10 
 
 5 
 
 
 
 3 
 
 6 
 
 " 13 
 
 11 
 
 
 
 ■ 
 
 4 
 
 7 
 
 782.. .Conditions to bk Satisfied in Aunam.im. a System of 
 "Minks. — As the galleries of a system of mines serve the pup* 
 pose of underground communications, they should he subjected 
 to the same conditions as other Communications. A condition 
 of primary importance is. that no combination shall be made 
 which might compromise the safety of the enceinte. To this 
 (iid, no gallery under the glacis should lead to the interior of 
 the enceinte; for, should the enemy get possession of such a 
 gallery, he might either penetrate into the work or else barri- 
 cade the gallery and hold possession of it long enough to blow 
 up the works under which it leads. 
 
 783. ..The galleries should not offer any facilities to the be- 
 siegers for carrying on their works. Those galleries, therefore, 
 which, debouching in the ditches, might serve the besiegers 
 fortheir descent of the ditch; also, a continued counterscarp 
 gallery, which may not only facilitate the descent of the ditch 
 of the besiegers, but, also, when in their possessionj give them 
 that of the whole sy.-tem, and, besides,' serve to protect their 
 passage of the ditch, and to prevent sorties in it, should be 
 rejected. A gallery behind a portion of the counterscarp not 
 
MINT-. 287 
 
 favorable to the enemy's works, is very useful as a depoi for 
 the implements of the miners, and also as a communication. 
 
 TW...A permanent system ef mines should not be osed, 
 either for works that can be carried by storm or for covered- 
 Ways in a similar state: for the reason that the besiegers 
 might easily get possession of the system before it could he 
 brought into play. 
 
 Z85.«.The debouch^ of a system in the ditches nnist he re- 
 vetted, to offer a sufficient obstacle to prevent the enemy from 
 getting possession Of the system by surprise; hence, a revetted 
 counterscarp is a necessary condition in the establishment of 
 the system. 
 
 7 v ''>...The galleries should not be run out to sxry considerable 
 distance beyond the covered-ways, both on account of procur- 
 ing a good circulation of air, and because very advanced gal- 
 leries are easily destroyed by the besiegers. Hie distance to 
 which the galleries may extend should he so much the ]. as, 
 the ground above them is well protected by the collateral 
 works. 
 
 787. ..The soil must be suitable for the establishment of a 
 
 tem; wet, marshy ground, shifting sand, and hard rock, 
 present almost insuperable obstacles; whereas, a (\vw firm 
 soil, soft roek. or ordinary earth under a thin superstratum of 
 hard roek, are very favorable circumstances. If the sub-soil 
 is wet. but ] i firm and dry superstratum 1 L' feet thick 
 
 ■bore the level at which the water collect.-, mines may still bo 
 placed with advantage* 
 
 788... Bi wd< - the above general condition*, then- are certain 
 • d to in arranging the galleries and 
 
 chambers. 
 
 The galleries should be placed a- far below the surf: 
 practicable, to withdraw them from the effect of the glolw 
 com of the 'P. drain the galler 
 
 should h _ht inclination, about 1 50, toward the ditel 
 
 or, if the -round <}■ . d a hollow . 
 
 may he given in that direction. 
 
288 mini fc 
 
 7^0. ..The chambers, on the contrary, should he near tlio ?ur- 
 face; by this arrangement the powder ia economized, and all 
 danger to the galleries from the explosion avoided; whilst the 
 object of the mines r whieh is to destroy the enemy's works, 
 can be as fully attained by small mines as large ones. 
 
 790..-Tij/e galleries should dot be placed nearer to each other 
 than twice the line of least resistance of the heaviest charged 
 mines, and not much less than four times the line of least 
 resistance of the smallest charges. This arrangement will 
 admit of a combination of mines in two tiers, the line of Lead 
 resistance of the lower being double that of the upper* the 
 chambers of which may be so arranged that the explosions of 
 one tier shall not affect either the galleries or the mines of the 
 other. Twice the line of least resistance of the largest mines 
 is the least distance that can be allowed between the galleries, 
 in order that the mines of the lowest tier, which, being placed 
 near one gallery, must destroy a part of it, shall not injure 
 those parallel to it. By placing the galleries at this least dis- 
 tance apart, the branches for the service of the upper tier will 
 be as short as possible, affecting thus a saving of time and 
 labor, and from the same cause the galleries on any one point 
 being as many as can be placed, there will be the advantage 
 that some one of the galleries will be serviceable should others 
 be injured by explosions. 
 
 791. ..The galleries and branches for the service of the differ- 
 ent groups of mines, should be Independent of each other, so 
 that there may be no confusion in the service, and that no 
 group may be rendered unserviceable by the destruction of 
 the communications to another. The same principle should 
 be attended to in combining the different groups of mine 
 chambers/ 
 
 792. ..The galleries and branches should never present their 
 flanks or sides to the globes of compression of the besiegers. 
 This rule leads to the rejection of enveloping galleries. 
 
 793. ..The systems of countermines proposed by most writers 
 on this branch of the defence are generally of too complicated 
 
MINKS. 289 
 
 a character to admit of being executed at a reasonable costj and 
 they require for their ■ service not only a large amount of 
 powder but also a great number of miners. 
 
 The following arrangement, based on the general conditions 
 jnst laid down, lias been proposed, to meet in a simple and 
 satisfactory manner the requisites of a subterranean defence: 
 
 Parallel to the capital of the demilune, four listening gal- 
 leries are run out to a distance of from 50 to 8<» yards beyond 
 the salient of the covered-way. The interval between these 
 galleries being twice the line of least Msietanee of the heav- 
 iest charged mines. If we take this line at 7 yards, or 21 feet, 
 which is about the greatest for common mines, the interval of 
 the galleries will l»e K> yards. The dimensions of the listen 
 ing galleries for about the first 20 yards may be those of a 
 grand gallery, and the remaining part may be a common gal- 
 lery. These galleries will depart from i transversal grand 
 gallery, about <"> yards from the demilune counterscarp, which 
 will serve as a communication between them, and also as ft 
 depot. Other transversals of the size of half gallern 
 branches, will be made at different intervals for the purpose 
 of ventilation. This group of galleries will have their outlet 
 into the demilune ditch through two gallei leading 
 
 from each extremity of the transversal grand gallery. I i 
 flank tliia group, other listening galleries will extend obliquely 
 outward from the two outside parallel gallera ] serve the 
 mines of thia group, a ding bra ''ill lead 
 
 from the galleries to chambers placed midway between the 
 galleries, having a line of l< if 4 yards. This 
 
 will place these chan about s yarda from I ad- 
 
 jacent galleries. Smaller branches may lead, it' necessary, 
 from these last branches to other groups of chambers, ha 
 a line of f cham- 
 
 bers with lines of lea 
 
 in juxtaposition wil i roti 
 
 rangemenl it will be readil; 
 i 
 
290 mi\ 
 
 Bxplpsions of the mines of one group will destroy the branches 
 and galleries which tead bo them, without injuring those 6f 
 other l:t« >u]>>. The object of this disposition is to blow up by 
 repeated explosions the ground over which the enemy must 
 approach apon the demilune salient place ef arras. 
 
 794...For the defence of the other portions of the glac 
 the demilune covered-way. a counterscarp gallery of the di- 
 mensions of a grand gallery is placed between the two traver- 
 ses next to the reentering place of arms ; a listening gallery 
 extends from one- extremity of tin's gallery in an obliqu^ di- 
 rection outward, and nearly parallel to the long branch of the 
 covered-way CFesf hetween the two traverses, to within BO 
 
 yards of the foregoing arrangement. Other listening galled 
 
 ies, placed l."> yards apart, run out from the main one, about 
 20 yards, to menace every point i>i' the glacis that can tie oc- 
 cupied by the beseiger's works. The groups of mines for 
 these galleries may be arranged like those of the combination 
 in advance of the demilune salient place of arms. The coun- 
 terscarp gallery should have two outlets in the demilune ditch ; 
 hut as these might compromise the safety of the whole 
 arrangement, should the besiegers attack the covered-way by 
 Storm, they must be walled up when the third parallel is com- 
 pleted, and the communication with the galleries then kept up 
 by a gallery leading to the main ditch. To supply the main 
 listening gallery of this group with air, a branch should lead 
 to it from a point of the demilune counterscarp under the tra- 
 verse next to the one of the salient place of arms. 
 
 iT9 5... Groups of gaUeriefi and mini's, similar to the one in 
 front of the demilune salient place of arms, may be arranged 
 for the defence of the bastion salient place of arms. And a 
 
 gallery, leading from the counterscarp oi the main ditch, may 
 he made for the service of a group for the defence of the glacis 
 of the reentering place of arms. 
 7'j<;...To defend the breaches made in the demilune and its 
 
 reddidit, a gallery may he made under the ditch of the re- 
 doubt, having its outlet in the main ditch; this gallery may 
 
MINIS. 201 
 
 divide into two branches, one leading under the demilune 
 breach, the other under thai of the redoubt. Ascending 
 branches may be made from the gallery leading to the demi- 
 lune breach, for the service of agroupof mines to blow up 
 the demilune terreplein. 
 
 7i»7... Finally, if the bastions arc arranged with interior re- 
 trenchments, a disposition similar to the one made for the 
 defence of the demilune may also be made for the defence of 
 the bastion breach. 
 
 T'. ,v ....\- the air in the galleries of mines is liable to become 
 foul from various causes; some mechanical contrivances and 
 chemical methods, by whioh the vitiated air can be removed 
 ami fresh air introduced, have to be resorted to for the pur- 
 pose of enabling the miner.- to circulate through them with 
 safety. Air pumps, bellows, and artificial drafts procured by 
 kindling afire at one of the outlets of a system of galleries, are 
 the ordinary expedients by which this object i*. attalried. 
 
 799.. .The great pecuniary outlay requisite in establishing a 
 system of permanent galleries, besides the large oorps o€ ex- 
 perienced miners and the extra provision of powder demanded 
 for their efficient service, when the system embraces any con- 
 siderable extent of surface, has led engineers to eon 
 
 whether the end proposed by Mil it '■rranean I defence 
 
 might not be attained by some more simple expedients, since 
 the application of galvanic current! to exploding mines, and 
 the facilities which it affords to effect this at very considerable 
 distances, it has been propose d to substitute ; - ■ for 
 
 galleries, placing them in positions m .Me to attain the 
 
 >rks. Tl :• ..f 
 
 permanency, may be lined with masonry, and r< 
 or iron cover which may be eonoealed from view I it pla 
 it several feet below th< When wanted for 
 
 the shafts are charge d and tamped in the usual i . and 
 
 connected with a galvanic battery by 
 ductors, laid sufficiently far b< 
 
 be without tl 
 
 ccrdents. 
 
292 ATTACK AND DEFENCE OF l'I KMAMNT WOBX8. 
 
 ATTACK AXD DEFEXCE OF PERMAXEXT WORKS. 
 
 FRENCH MATERIALS. 
 
 1... Under this head arc comprised the materials used by 
 tin- besiegers for revetemenis and covers against the fire of the 
 defences. 
 
 Fa-, im:-. These are usually made 18' long, and 9" in 
 diameter, and are afterward cut into suitable Lengths for the 
 purposes to which they are to be applied. 
 
 Pickets. Those used for securing fascines are from 2' to 4' 
 long, and from 1^" to If" thick ; those for setting out or tracing 
 the works are 18" long and 1" diameter. 
 
 Sai'-i-a<;<>'js. These* are made, like fascines, of straight brush- 
 wood at least 1" in diameter. They are -' '•'" long, and 9" in 
 diameter. The centre stake should he from H" to 2" in diame- 
 ter, and project \)" beyond one end of the Bap-fagot; this pro- 
 jecting portion is sharpened, to enable the sap-fagot to be 
 planted firmly in the ground in an upright position* 
 
 Gajjions. The exterior diameter of these is 2', and the 
 height of watling is 2' 9". They arc made with seven or nine 
 stakes, which project 6" above the watling at top, and ap- 
 pointed. 
 
 At the siege of Sebastopol, the want of brush-wood for the 
 watling of gabions led to the introduction of the common 
 hoop-iron, fof this purpose, which had served to secure the 
 bales of hay. The number of pickets employed fo? each gabion 
 was usually thirteen. It was found that these gabions could 
 be constructed more readily than the ordinary kind; that they 
 were not much heavier, more durable, and in all respects as 
 serviceable. Since then, it has beeu proposed to use simple 
 
ATTACK ANIi DEFENCE OF riKM.Wl.vi WORKS. 
 
 Bheet-iron cylinders, of suitable dimensions, instead of the 
 brush-wood gabion. For this purpose, rectangular sheets of 
 iron, of suitable dimensions to form cylinders of the same 
 height and diameter as the ordinary gabion, arc prepare/i* 
 with three or four holes flinched near and parallel to the 
 shorter sides of the sheet to secure these ends with wire when 
 the sheet is bent into the cylindrical shape. Besides tie 
 tw<i other holes of larger size are punched toward the central 
 portion of the sheet, ao as to be diametrically opposite when 
 the cylinder is formed, to receive a picket passed through 
 them- which serves as a handle in carrying the gabion. The 
 advantages of this description of gabion are greater strength, 
 lightness and durability than either of the others; offering 
 great facility for dbtant transportation, and resisting bettor 
 the blast of guns when used for revetting the cheeks of embra- 
 sures, 
 
 Sap-boi^j i;-. This i.- a large gabion, 7' <i" in length, and V 
 4" exterior diameter. It requires (or its construction fifteen 
 ■takes, each from 14/' to 2" in diameter. After it is completed, 
 it is stuffed compactly with fascines 7' <;" long. The sap-roller 
 is sometimes made df t*vo concentric gabions, the diameter of 
 the smaller 2* *>". The space between the two is compe 
 stuffed with i 
 
 S.\M-i;\o-. Tie- mu d-bag, for the revetement of battel 
 when empty and laid flat, is 2* s " Long and 1' 4" wide : r 
 used in the construction of the trench* i are _' long, l_" « 
 
 r.uM>\oi -i k wii -. These frames, Pi. to, Fig. I, are com- 
 posed of two uprights, or stanch cantling, 
 <;" long, and pointed at both end*; and two horizontal pit 
 of the same Bised scantlii i 
 piea tr-lied npon I 12" from i a< b • 
 The width of the frame from out to out is 3' \" : the • 
 between the horizontal pi< <■< - from onl to 
 
 An auxiliary ■' 
 used in | • be blindag* fran • 
 
204 ATTACK AND DEFENCE OF PERMANENT WOHK&. 
 
 Ctai.i.i'ky-i i: \mi<. The arrangement and dimensions of these 
 are the same as those used in mining. 
 
 TRENCHES. 
 
 2. ..The term f/v/ir/i is applied to an excavation or ditch made 
 by the besiegers, by means of "which", and of the earth thrown 
 from it, they are enabled to obtain speedy cover from the tire 
 of the defence's, and to approach them with security. 
 
 Trenches are divided into two principal classes — the paral- 
 lels and the approaches. The parallels are designed as stations 
 for troops to guard the trenches, and the workmen employed 
 in their execution, from the sorties of the garrison. The ap- 
 proaches serve simply as covered communications which lead 
 to the parallels, and toward the points of the defences upon 
 which the attack of the besiegers is directed. 
 
 The general direction of the parallels is parallel to, or con- 
 centric with, the line connecting the most salient points of that 
 portion of the defences attacked. The approaches are run in 
 a zig-zag, or in a straight line, upon some or all of these points. 
 
 SL.The trenches of the parallels, P1M0, Figs. 3, 4, 5, 6, re- 
 ceive a width at bottom of 10' ; their depth in front is 3', and 
 in rear 3' 0". ' Two steps, each 18" high and IS" wide, lead 
 from the bottom of the trench, on the front side to the natural 
 ground. The reverse of the trench receives a slope of 45°, or 
 else, is also cut into two steps. The steps in front are alone 
 revetted with fascines. The trenches of the approaches, PI. 
 10, Figs. 7, 8, are 8' wide at bottom, .".' 6" deep in front, and 1' 
 at the rear. The reverse receives a slope of 45°. The front is 
 usually made with a slope of 2' base. 
 
 The earth from the trench is thrown to the front to form a 
 parapet. The general height of this parapet is nearly 5', its 
 width at the base about 18'. 
 
 4...SiMPLK TitK.veii. AVhen the parapet is formed of earth 
 alone, Figs. 3, 4, 7, the trench is termed a simple firendh. In 
 this case the earth of the parapet is allowed to take its natural 
 
ATTACK AN1> IM.HVI OF I'lKMAM.VI WOBEB. 295 
 
 slope on the side toward the trench. Xhostep, orberm, of l v ", 
 between the fodl of the parapet and the trench in the parallels 
 serves as a banquette. 
 
 Portions of the parallels, Figs. 4, fi, from 20 to 30 yards in 
 length, are arranged with steps, revetted with fascines, lead- 
 ing from the trench over the parapet, to enable the troops in 
 tlic parallel to debouch from it against a sortie. 
 
 The direction of the trench is laid out by pickets, connected 
 Ox white tape, which is marked off into Lengths of 6' by short 
 pieces attached to it. The trench is executed by Soldiers of 
 the line ; each man being furnished with a pick and shovel, 
 with which he excavates 0' in length of the trench, and as 
 much of it to the rear as may he assigned to the relief, or 
 
 working party, to which he belongs. After the trench has 
 
 received its general width and depth, the slopes and ?>tcps are 
 finished off with the asnstance and under the direction of the 
 engineer troops. 
 
 .V..I'mi.\<, Sap. AVhen the trenches have Leen pur-hed for- 
 ward to within destructive range of case shot, the construc- 
 tion by the simple trench has to l.e abandoned, and one which 
 will afford more spei -dy shelto r resorted to. This is effected, 
 5, v . by placing ;i row of ordinary gabions in juxtaposi- 
 tion, along the direction of the trench ; these being filled with 
 tlie earth from the trench, the parapet i> completed by throw- 
 ing the remaining earth over and beyond them. This pw 
 
 rmed the living sap, from the rapidity with which the 
 Work i> done. It. also, U executed by troops of the 1; 
 man bringing two gabions on the ground, which he i> requi 
 1. and . the portion of the trench, in 
 
 rear of them, assigned to the relief to which he belong 
 requisite height to tin- parapet either by heaping 
 
 the earth ab< ' by plac 
 
 dinary :.. ipon tin -. two being in the botl 
 
 cour-' and th( ' cm top, and I 
 inc. 
 
 In | 
 
296 ATTACK AND DKVEOffCB OF PF.UMANT.XT WORKS. 
 
 quantity to afford a speedy cover, as in a shallow stratum of 
 soil on rock, etc. two rows of gabions; placed in juxtaposition, 
 may be used tor the flying sap. 
 
 The troops tor constructing both this and the simple trench 
 aiv divided into three parties, or relict's. The first* digs the 
 trench to the requisite depth and to the width of .V; the second 
 widens it 4' G"; the third tinislies what remains, giving the 
 requisite slopes to the front and rear. 
 
 EtsMASK. The dimensions and form given to the profiles of 
 the parallels and hovanx in the preceding paragraphs are those 
 used in our own and the English sapper practice. The French 
 allow usually 3' 3" for the uniform depths of both, and 4' 3" 
 for the height of parapet. This gives a cover of 7' G" in the 
 trench, which would seem ample, whilst it gives the parapet 
 a more suitable height for the convenient delivery of the fire, 
 if the troops stationed in the parallels are called upon to repel 
 a sortie in this way. 
 
 G...Full Sap. The full sap, Figs. 9, 10, 11, is resorted to 
 when the fire becomes so destructive that the living sap can- 
 not be used. The trench is opened and pushed forward l>y 
 engineer troops alone ; for this purpose a working party, 
 termed' a. brigade, of eight sappers is requisite. The brigade 
 is divided into two equal sections; the sappers of the first 
 section dig the trench, and arc numbered from 1 to 4, No. 1 
 leading. The other four arc termed assistants; they bring 
 forward the materials, and assist the first section in all the 
 necessary operations. 
 
 The leading sapper, No. 1, is provided with a pick and 
 shovel, and wears a musket-proof helmet and cuirass; he 
 works on his knees, being covered, on his side toward the de- 
 fences, by the parapet of the trench, from which he debouches, 
 and In front by a sap-roller, which is placed perpendicular 
 to the line of direction on which he is to work, and rest* 
 auaiust the gabion he is filling, covering it one foot. The por- 
 tion of the sap which he digs is 21" wide at the top and L ; l" 
 deep ; it receives a slope of 4 perpendicular to 1 base on the 
 
ATTACK AND DKFI.XCI OF ITKMANTWT WORK. 207 
 
 front, and is vertical in the rear; and its length is .V. Softool] 
 as this portion is finished. No. l\ who is projected in all 
 like No. 1, commences to widen and deepen the trench s" at 
 the point from winch No; 1 started, and follows on after No. 
 1, keeping alsravs 5' in his rear. When X<>. 9 has pu.-hed for- 
 ward .">'. No. 3 commences and enlarges the trench in each di- 
 rection 7"; he follow* on also 5' in rear of Ne. 8j hut as the 
 work thrown up by the sappers preceding him affords pretty 
 good cover, lie can work standing, taking the precaution to 
 bend forward for gr curity. Finally, No; 4 bej 
 
 when No. 3 lias got on .V, and deepens and widens 7". As he 
 is well covered, he can work in an unconstrained posture. 
 
 lea the shelter given by the gabions; as they are suc- 
 
 welv filled, and the sap-roller, the further precaution is 
 
 taken of •'driving sap-1 Long the berm, a1 the junction of 
 
 the gabions; these are successively removed as they are no 
 
 _ i- requisite. The trench fascines are placed upon the 
 
 gabions by the assistants, and the remainder of the trench 
 
 completed by working parties of the line, so soon as the 
 brigade of sappers have proceeded far enough for tin.' others 
 to commence without hindrance. 
 
 7...1)<Tm.i Bajb. This sap, Figs, L2, 13, consi-t.- of two 
 h«-ad.- of sap pushed forward by two brigades working abreast 
 It- object i.- to form a trench in a position • both 
 
 sides to fire. The head of the sap is covered by two sap- 
 roller.- placed end to end; a bag of wool, or a short .-ap-roller, 
 being placed at their junction, for additional security.' . 
 distance between the two rows of gabions is 1-'. arth 
 
 between the two line.- of |gp fa removed by the usual 
 parties, a- in the prei 
 v.. 1 1 i : Sap. <>f full i 
 
 1 J, pushed forward in a 
 
 temporary cover on the r< verse of th< 
 filled with sand-bags. I 
 gabions, in 1 
 Log in front this interval Iron .re. 
 
298 ATTACK AM» I'll I.N.I. Q» I'IKMAM.M W0SXB. 
 
 9...Di:fji.i.mi:n t ok Tki .wins. The position given to the lines 
 of the parallel, and the dimensions adopted for its trench and 
 parapet, give ample cover to the troops in it from the plung- 
 i n g fire of works having anything like the usual command. 
 But in the zig-zag approaches,' or boyaux, as tlie line of the 
 trench has to be directed toward the defences, it is necessary 
 cither to defile the trench, by giving it a direction such that 
 the lire, coming over its parapet, will not have a plunge sutfr- 
 cicnt to attain a man standing in the reverse of it, or, when 
 this cannot be done, by placing traverses along the line to be 
 covered, Which shall effect the proposed end. 
 
 In the usual cases of practice, the ground on which the ap- 
 proaches are run will be more or less uneven, and this in- 
 equality of surface, if quite appreciable, will demand a corres- 
 ponding variation in the line of direction of an approach, 
 where its defilement is to be effected by the position given to 
 it with respect to the point from which it may be attained by 
 the enemy's fire. In most cases, however, each portion of the 
 line of the trench, corresponding to the changes in the surface, 
 may, without any very great error, be regarded as lying either 
 on a horizontal, or an inclined plane; and, in the latter ease, 
 the plane may either rise toward the dangerous point or 
 descend in the same direction; there will, therefore, arise 
 three cases of defilement, according to the position of the 
 plane on which the trench is run with respect to the dangerous 
 point. 
 
 To illustrate these cases, let the approach to be defiled, be a 
 trench constructed with the Hying sap. Now, whether the 
 ground be horizontal or inclined, the relative position of the 
 lines of the profile of the approach should be preserved as 
 nearly as practicable. The vertical height of the top of the 
 parapet — supposing the latter no higher than the top fascine — 
 above the bottom of the trench, at the reverse side, Figs. 15, 
 16, 17, will then be 8' 3"; and the horizontal distance between 
 the same points 12'. Now, in order that a man standing at 
 the reverse of the trench may be secure, the line of fire of the 
 
ATTACK AXD DBFEITOE'OP PERMANENT WOH 291) 
 
 enemy should not have a greater plunge than 6* f>" above the 
 bottom ofthe trench at this point. Tin's will limit the inclina- 
 tion of the line of fire to the horizontal dfawn through the 
 top- of the parapet to about 1 perpendicular to 7 bate, or an 
 
 angle of 1-fi It will readily be Been from this that the. line 
 of the trench must nol be run so near the dangerous point 
 that the line of tire from it, passing through the top point of 
 the parapet, and in the direction ofthe profile of the trench — 
 that LB, in a vertical plane containing the dangerous point, and 
 perpendicular to the horizontal projection of the line of the 
 trench — shall make a greater angle than 1-7; and that, when 
 the line ofthe trench satisfies this condition, it will be defiled 
 by its position. 
 
 To Fi\i» Tin DsrtLBB Position op a TWekch oh Bfoattbir* 
 tal Groino. Le4 I>. Pig. I s . be the point of departure of 
 an approach leading from a parallel, and C the most dan- 
 gerous point of the defences for this approach, the height of 
 which above the parapet ofthe approach is known. It is evi- 
 dent, from what has just been laid down, if the approach were 
 continued on beyond the point C\ and a line with an inclina- 
 tion of 1-7 were drawn from Q perpendicular to the direction 
 ofthe approach and through the top of its parapet, that a man 
 Standing at the reverse of the bottom of the trench would not 
 
 be attained by this fire i but m the top of the parapet, or in- 
 terior creal of the approach, is horizontal, and the reverse of 
 
 the bottom of the trench is parallel to it. it is farther evident 
 
 that the plane which passes through the point and the in- 
 terior crest of the approach, will pass at the same height ab 
 e\. tv point of the n I the bottom of the trench that 
 
 me of 1-7, through ('.<]■■ the point < < . 
 
 line lies in the plane ; it. tie-: at. if the ] 
 
 defiled, i ther point along the i rich 
 
 will also be defile L. To c ■ itract the position of the Lift /' 
 
 tiv. w Lth a I.e. i- • | . . ' - vertical he 
 
300 ATTACK AMi DEFENCE OF l'l.KMAXKNT WORKS. 
 
 above the parapet of the approach, an arc of a circle, the tan- 
 gent to this arc from 1> will he the required position* 
 
 .\..ii. Iii Fxgi I s . the dangerous point, C. is 18' above the 
 horizontal plane of the trench. The reference of this plane 
 being (0), that of the point 6' is (18.0), and that of the inte- 
 rior crest of the approach ii 1 4;25 i. Tin- reference of the point 
 a is (11.0); the declivity of the glacis planes 1-21. 
 
 10. ..To 11.NI> illl .1)1. HI. in I'wHTloN oK AN APPEOACB o\ Ix- 
 n.i.NED Grouni'. l.ci. Fig. IS, two planes of a glacis inter- 
 tcrseeting in a ridge, a J, one of the planes rising in the direc- 
 tion of the dangerous point C\ and the other falling toward ir, 
 he taken as the ground on which the trenches are to be run ; 
 and let A, at the foot of the plane which ascends towards 6", 
 be the point of departure of the approach. Now, the plane 
 being produced toward 6' may either pass above it, through it, 
 or below it ; in either of the two first positions it is evident, if 
 the interior crest of the approach were directed on the point 
 6', that the trench would be defiled; for no line of tire from 
 C would, in cither of these cases, have a plunge into the 
 trench, and the same would hold true if the plane produced 
 passed at a distance below it just equal to the height of para- 
 pet of the approach. In either of these cases, therefore, to 
 defile the trench, it will only be necessary to direct its interior 
 crest on the dangerous point, and this direction may be kept 
 until the approach strikes the ridge at B. 
 
 11. ..At this point, as the plane of the glacis on which the 
 prolonged branch of the trench is to be run descends toward 
 C, and is seen in reverse by its fire, it will be necessary to 
 change the direction of this branch so as to withdraw it from 
 the plunging fire from ('. This will be effected by giving this 
 branch a direction such that a line of fire from O, having an 
 inclination of 1-7, ami being contained in the profile plane of 
 the trench which passes through c7, shall clear the head of a 
 man standing in the trench at the reverse side; and this will 
 be the case if this line of 1-7 passes through the interior crest 
 of the parapet and 6' 0" above the bottom of the trench at the 
 
ATTACK AND DEI- 1 \< B OF IM KMAMM WOE 301 
 
 vcvorso. It is evident, in die first place, tli.it this will be true 
 for the profile plane through C. Now, since the line of the] 
 interior crest and the line of 1-7 intersect, they will determine 
 a plane which passes through (\ and in which all the lines of 
 fire from. (' which strike the interior crest are contained. As 
 the reverse line of the hottoin of the trench is parallel to the. 
 interior crest, and as the plane of fire in (]iie>t ion passed ;it d' 
 c," above that point of the reverse line of the hottom which is 
 contained in the profile plane through C, it follows that, this 
 •lane also passes at G' 0" above every other point of this re- 
 ver.-e Line. :nid. therefore, that the direction of the trench 
 which fulfils this condition will be defiled throughout from the 
 fire coming from C. 
 
 onstruct this position, let the point Cbe taken as the 
 vertex of a right COhe, the elements of which make an angle of 
 1-7 with its base. The line of fire of 1-7 will be an element of 
 this cone. If the com- be intersected by a plane parallel to 
 the one on which the approach is run. and at a distance above 
 it equal to the height of the parapet, the interior crest of the 
 approach must intersect the curve cut from the cone by this 
 place ; and. to satisfy the conditions imposed, the point of in- 
 
 Ctiton must he where the projection of the element of the 
 
 cone is perpendicular to that of the interior crest) 
 the relative positions in projection of the line of tire of 1-7 and 
 of the approach. To construct the projection of the curve cut 
 from tic cue. it will only bt try to intersect the i 
 
 and plane by equidistant horizontal planes, and to find the pro- 
 ions of tin corn spending point.- of ml n of the 
 cut from the two surfaces by tin se plain -. To find ti 
 tion of the approach, join the point of it> departure . /»'. with 
 
 ad oh this line describe a semicircle : the p.. 
 this semicircle cuts the projection of the curve cut from 
 ie required direction, />' T. of the approa 
 A lik< e, : struction \\ onld : 
 on an osc< riding plane pas* - 
 
302 attack ani> DJFENCE off im'km \m:n I WOBX& 
 
 tance than the height of the parapet below the dangerous 
 point; 
 
 12...I1 will be noted from what precedes that the approach 
 is never directed within a dangerous point ; for the obvious 
 on tliat. it' so placed, it would he exposed to reverse fire 
 from die point If it should happen that the direction ]> X. 
 found tor the approach in the preceding ease, would bring its 
 prolongation within a dangerous point. (\ on the Left of the 
 ridge* toward which tin- plane ascends, it would then bem 
 saty to change the direction B X to that of C B X\ and. as 
 this would expose the trench to a plunging lire from Q it will 
 be farther requisite either to deepen the trench, or to raise the 
 parapet higher, to cover the reverse from this plunge. 
 
 1".... It will he farther noted that, at the point of departure 
 of an approach from a parallel, there will he a portion of the 
 parallel, j> y. in the rear of the trench, which will not he fully 
 covered l>y the parapet of the approach. This portion will be 
 limited hv the line of tire from 17 through 0, where the reverse 
 of the approach cuts the interior crest of the parallel; and l.v 
 the reverse prolonged to <j. To secure this portion, either the 
 Wench of the parallel naasl be deepened or that part of the par- 
 apet of the approach be raised, which is intercepted hetween 
 the lines of lire from C on j> and <y. 
 
 14... I )i:I']li:mi:nt i:v Tkavkksks. When the defilement can- 
 not he effected by the position given to the trench, resort must 
 be had to traverses. Two cases present themselves under this 
 head : one in which the reverse of the trench is exposed to a 
 very slant lire; the other in which the trench is pushed for- 
 ward hetween two dangerous points, and is, at the same time, 
 exposed to an enfilading lire. 
 
 15. ..In the first case. Fi^. 19, the trench is carried forward 
 by means of the half-double sap. So soon as the head of the 
 sap has been advanced the length of twelve gabions beyond 
 No. 4, a short end of sap, termed a winy traverse^ is com- 
 menced in a direction perpendicular to that of the trench, and 
 run out until it intercepts the line of lire upon the point of'de- 
 
ATTACK AM» l-l I I M I 01 II KMAM'N'I WOBKS. 303 
 
 partnre at the distance of twelve gabions in it- rear. When 
 this end of Bap Id completed, the provisional parapel in its 
 roar can be taken down ami the trench enlarged to its proper 
 width. In tin's way the trench is successively pushed forward 
 and enlarged, until a position had been reached Where it be- 
 comes necessary to place a traverse to cover the trench from 
 both enfilading and rovrrtr views. These traverses, .1. .1. 
 made by changing the direction of the trench perpendicular to 
 that of the original line, and continuing in this new direction, 
 by the full sap, the requisite length of the traverse : the origi- 
 nal direction is then resumed, and continued, by the half*double 
 sap, a sufficient distance to leave room For the width oil the 
 traverse ami a trench of double sap ; another rectangular turn 
 is then made, by the doable Bap, hack to the line of gabions of 
 the original tn nch, and the original direction is again taken 
 up and carried forward by the half*dottbl< Bap. 
 
 The ti;. I.J. are Bey%n gabions, or about 14' in width. 
 
 Their length will depend on the position of the dangerous point, 
 but the\ Ion made over 9& in length. Their distance 
 
 apart will also depend on the command of the dangerous point. 
 The portion of trench between any two traverses must he per- 
 fectly covered by the advanced travel---. A- i practical rule, 
 the traverses are not placed farther than 26 or 80 yard- apart. 
 
 The portion of the trench, II. in rear of the end of the trav- 
 . >vered by extending sufficiently far to the rear of it an 
 end <>f trench, ( '. fori | the line 
 
 of dan) fire. 
 
 !■;... In 1 90* the trench, ^,ie carried fi 
 
 ward by the double sap, until the point of departui 
 about being expose d to the fire cominj 
 a chfl .'...- 
 
 full sap, to the right 
 
 about ti:' . when the original i . />. bi 
 
 doub lumed. A i 
 
 made both to th' 
 direction, by the full 
 
304 ATTACK ANT* DEFECT V. OF IT.KMAMNT WORKS. 
 
 or fourteen gabions. Then, from the extremities of these 
 hranche.-, a direction parallel to tin 1 Original is taken up by the 
 double sap. and pu^ied on until the point of departure is about 
 being etposed, when a change of direction is made at right 
 
 angles by the! full sap. and the two branches are united on the 
 original direction, A] which is resumed by the double sap. 
 
 17...Ti:r.xcii C\\\Ai.u:ii. This work consists of a parapet 
 raised on a mound of earth, for the purpose of obtaining a 
 
 plunging tire on the covered-way. The mound should, in all 
 ca>cs, be raised so high that the cavalier will have a command 
 of -i-^ feet over the crest of the covered-way. The position of the 
 cavalier is shown in PL A, Fig. 5. When the trenches are ad- 
 vanced liv the full sap nearly within reach of grenades thrown 
 by hand, or about 30 yards from the salient, <i< of the covered- 
 way, a circular -portion of trench, b c, is formed, to embrace 
 the production of the crests of the salient; from the extremi- 
 ties of this circular portion the sap is run perpendicular to the 
 direction of the crests, to a distance, c d, of about 8 or 12 
 yards, so as to enfilade the covered-way; at the extremity, </. 
 a win*/ or /(turn, d e, is made to cover the part, o </, from the 
 flank and reverse fire of the collateral works; this part, 6? d, 
 may, in some cases, be arranged nearly parallel to the crot- 
 chets, n o, of the covered-^iy, so as to give a fire on them; 
 but generally it serves onlj- to cover the branch, c d, as has 
 been explained. 
 
 18. ..There are two ways of forming the cavalier, depending 
 on the nature of the soil. When the excavated earth is pi 
 such a nature that it can be easily made to stand at any slope, 
 a pi-olile, represented by Fig. 21 , is preferred, as requiring less 
 time and materials. After having laid out the position of the 
 cavalier by the full sap, the sappers wixlen the trench il', and 
 make a step at the bottom of the trench 22" in height, and 
 5' 0" within the gabion of the parapet; this step serves as a 
 platform on which the sappers mount to level the earth of the 
 parapet even with the fascines on top of the first gabion, for 
 the purpose of placing a second tier of gabions, which is placed 
 
ATTACK AND DEFENCE OF PERMANENT W0BKS. 305 
 
 22" beyond tlio first. This second ten- IS filled with earth, and 
 crowned with two fascines, and the mound is raised to a level 
 with the fascines, by widening the trench to the rear. The 
 
 earth is now levelled even with the top of the faaCUieB, and a 
 third tier of gabions is placed just, on the outside of the second ; 
 it is filled with earth, crowned with three fcsoinea, and the 
 mound is raised to a level with the upper fascine. Thif t-.p 
 tier forms the parapet of the work. Loop-holes are made 1 » v 
 arranging sand-bags on top of the parapet, for the purpose of 
 covering the heads of the aieii whilst in the act of firing. As 
 the successive tier.- of gabions are placed, Steps, revetted with 
 fascines, are made to lead to the top; these steps have a 
 %nd tread of 22" J the top one u a banquette. f 
 
 It). ..When the soil eXCftV&ted i. loose, a cavalier made in the 
 manner jttst described would ool be sufficiently firm. Hie fol- 
 lowing construction will in this case be used ; After having 
 traced out the cavalier by the full sap, a row of gabii 
 22, is placed in the bottom of the trench, along the foot of the 
 interior slope; this row is tilled With earth, and crowned with 
 two : . and earth is filled in between it and the interior 
 
 slope, and brought to a level with'the berm. A third tier of 
 gabions U placed on this platform, alongside of the row form- 
 ing the parapet of the trench; this tier is, in like manner, 
 
 filled with earth, and crowned with two fa 
 
 tier of the cava) >oamenoed, by placing a fourth row .,f 
 
 gabions over the joint of the two in the fj 
 
 with earth, crowned with two B, and the mound 
 
 on the exterior tp a level witty this fourth gabion. >\ fifth 
 
 \t placed al< of the two in the first tier, filled with 
 
 earth and crowned with I - ii is then pis 
 
 aloi the fourth, in the second tier, and arranged like 
 
 the preceding, i inally, tie 1 parapet is formed on this t& 
 tier, by placing a gabion above the joint bet* 
 
 nd tier, and ai 1 7. 'I 
 
 made to Second to the 1"]', by tin .irth, 
 
 30 
 
306 A1TA< K ASD Mil N< E OF PERMANENT W0KK8. 
 
 on the interior, against the gabionade, and forming the surface 
 into steps revetted with fascines, as in the last case. 
 
 DESCENTS OF THE COVEEED-TVAY AND DITCHES. 
 
 20...I'>i.im»i i> 1>is( knt. "When a trench has to he pushed 
 forward in a position where the command of the dangerous 
 point is so great that it cannot be sheltered from the plunging 
 fire by traverses, it is covered on tli'c top and on the Bidea by 
 fascines and earth supported by a framework, and is termed a 
 hi 'i ullage. 
 
 But this method of obtaining cover is principally requisite 
 in trenches which descend toward the dangerous point ; like* 
 the passages which lead from the trenches on the glacis into 
 the covered-way, and to the hottoms of shallow ditches. The 
 manner of forming the blindage, Figs. 2o, 24, is to set up a 
 row of blindage frames along each side of the trench or pus- 
 sage; to connect the two rows at top by like frames laid across 
 the line of the trench; to cover the top frames by fascines and 
 earth; and to fill in between the side frames and the sides of 
 the trench with fascines. The trench is made by the double 
 sap. Its width at bottom is 7' 6". The width between the 
 frames, 6'. The frames and fascines of the blindage are grad- 
 ually placed as the trench advances, the latter preceding the 
 former about 5'. The work is begun by placing an upright 
 frame on each side; the two are next connected by a frame on 
 top, one side of which is lodged on the top cross pieces of the 
 upright frames, and the other supported by two auxiliary 
 frames until the next two upright frames are placed; the fas- 
 cines are then thrown over the top frame to the depth of 
 about 2', and these are covered with earth or raw hides, to 
 prevent their being set on lire. Fascines are at the same time 
 placed in on the sides. 
 
 The slope given to the bottom of a blinded descent should 
 not be greater than \. "When the descent is to a covered-way, 
 Figs. 23, 24, the bottom of it should debouch into the covered- 
 
ATTACK AND DEFKNVK OF I'KKMA \ 1 NT WORKS. 307 
 
 way at -1."." below its terrepleia ; this will serve to determine 
 the point of departure, the Blope being iivd. which Bhould be 
 ;>' below tlie surface of ilie glacisj ^o that when the blindage 
 is put np at this point the top of it shall not be above the level 
 of the, parapet of the trench. A horizontal landing about 8' 
 in breadth, is made at the en trailer of the blindage; add this is 
 connected with the bottom of the trench by two rani])- of 1-<I. 
 
 The point selected for B Minded de.-celit into a coVeivd-way 
 is usually at the end of a traverse: as the traverse will oover 
 the outlet of the blindage from a plunging fire in front. 
 
 21. ..A descent to a ditch is usually hy blindage, when the 
 depth of the ditch does not exceed l'T or 12'. For 
 depths the commencement <>f the descent is by a blind 
 Fig. 25, which is continued to a point where the bottom of the 
 descent is about U' below the surface of the ground; here the 
 blindage is terminated, and the remainder of the descent is 
 made by gallery, as the depth of the earth above the gal 
 will be sufficient to allow the excavation to be carried on with- 
 out trouble. In a firm soil, grand gallery frames are used for 
 the descent ; in a loose soil, common gallery frames. The con- 
 struction of the gallery is the same as for a mine gallery. 
 
 The point of departure of a ditch descent is usually I 
 at only about 2' below the bottom of the trench; the usual 
 landing being made at this point. In a (\ry ditch, the bottom 
 of the descent debouches at the usual depth of the tail sap 
 below the bottom of tin- ditch. In a wet ditch, it should come 
 out about 1.7' above the water level. 
 
 I' IBS \<,I - OF MT< 111 9, 
 
 •_'_'.. . I >i: v Ditch. The: if a dry ditch is nothi 
 
 than a full sap. which leads from the on; t in 
 
 the ditch to the bottom of ' I h. From this l 
 
 trench and parapet are din ct< d np» the brei 
 wall, which foro 
 «.n- point. The onl\ 
 
308 ATTACK AND DEFKN.'i: Of PERMANENT WoKKS. 
 
 sage is, to sink the trench at the outset to its full depth of 4:5" 
 to gs&n secure cover- 
 
 23...AV i i DncH. The passage of a wet ditch is a perilous 
 and difficult operation trader any circumstances, but particu- 
 larly so when a strong current can be produced, by the be* 
 d, in the ditch. The methods usually recommended arc 
 to form a dike, or bridge of fascines and hurdles, laid in suc- 
 cessive layers, and firmly connected by pickets. To form a 
 footing tor the dike, a grand gallery is excavated, directly be- 
 hind the counterscarp wall, to a distance of 12' or 15' on each 
 side of the descent, and the earth from it is thrown into the 
 ditch, through the outlet of the descent. The dike, or bridge 
 of fascines is gradually pushed forward from this point, being 
 secured in the best way practicable to the earth thrown into 
 the ditch. The sappers who carry forward the head of the 
 dike are covered from the fire of the dangerous point by a 
 musket-proof mask of fascines and boards, attached to a raft 
 on which they work. The (like should be from 12' to 15' wide 
 at top. A gabionade parapet is placed on it toward the dan- 
 gerous side. It is formed of two tiers of gabions, tilled with 
 earth. The bottom one consists of two rows of gabions, each 
 crowned with two fascines — the two rows being in juxtaposi- 
 tion ; the top tier is a single row crowned with three fascines. 
 The top of the dike is covered by a layer of earth, and the 
 parapet with raw hides, to prevent the effects of incendiary 
 compositions that might be thrown on them. Raft-bridges, 
 on barrels, protected by a gabionade parapet, have also been 
 proposed, particularly where a strong current is to be contend- 
 ed with. 
 
 BATTERIES. 
 
 24... Enfilading and Counter-batteries. These batteries 
 are used for destroying the artillery and silencing the fire of 
 the defences. Positions' are chosen for the first from which 
 the terrepleins of the faces, that bear upon the ground on 
 which the parallels and approaches, are laid out, can be en- 
 
ATTACK AND DEI 1 \< I OF PERMANENT WORK8. 809 
 
 filaded ; the second are so placed that they «:ui bring a direct 
 or a slant fire against the embrasures of the points to be 
 silenced. The shot from the former la thrown with small 
 charges, under angles of elevation <>f from 0° to 1>°, so as to 
 ricochet along the terrepleins, taking the guns of tin* defences 
 in flank; the latter fire with full charges directly against the 
 j.oinl to be attained. 
 
 25... As the effects of both direct and enfilading lire vary 
 greatly with the range, positions should be chosen for these 
 batteries as near the defences as they can he tlimwn np with- 
 out too great a sacrifice of life. Positions which will give 
 ranges between 3(J0 yards and 7"<» yards, are the best i nearer 
 
 than 300 yards, the workmen would be exposed both to the 
 
 Are of musketry and case shot: beyond 7"*" yards, the lire 
 upon the defences becomes very uncertain. The besl points 
 for these batteries are, therefore, on the tone of ground occu> 
 pied by the first and second parallels; the former being at 
 about i'xmi yards, and the latter about 8Q0 yards, from the 
 most salient points of the defene. 
 
 96.. .The batteries may be placed either within the parallel, 
 in advance of, or in rear of it. The positions usually selected 
 
 are from 20 yards to 80yards in front of the parallel; because^ 
 
 if placed within it. there might be mutual interference be- 
 tween the service of the batteries and that of the parallel : i 
 unhss placed soi listauce iii the rear of it. the parapet of 
 
 the parallel might obstruct the shot of the battery, and the 
 
 troops in the tr< neb be annoyed by the fire. 
 The most effective positions for these bati i 
 
 of the second parallel; and unless ti 
 
 very destructive, it will l.e beat to plaoc them th< re. If 
 
 placed in front of the first parallel, it will be necessary 
 
 the most Of them to the liv-nt of ' 'd "parallel » 
 
 after the latter is thrown up. For the third parallel. 
 Hppr ading to it from the second parallel, run I 
 
 of being attained by shot from ba 
 in their i be first parallel. 
 
310 ATTAriv AMD m.lT.XCK OF rEItMAM XT WolJK-. 
 
 27. ..The site of the platforms of the batteries may cither he 
 on the surface of the natural ground or sunk below it. In the 
 latter case, the battery is termed a sunken battery. In the 
 former case, the parapet of the battery is obtained from a 
 
 ditch in advance of it ; in the latter, it is got from a trench in 
 it> rear. In the sunken battery, the labor of construction is 
 lees, and the men engaged in making it are placed more 
 dily under cover than in tic other kind. Sunken batteries 
 can only he ttsedj however, when the trenches, or other ele- 
 vated points, in advance of the batteries, which lie in their 
 field of tire, will not intercept the shot; and, as a general rule, 
 these batteries should be placed only in positions where their 
 field of fire is completely unobstructed by the trenches. 
 
 28.. .The interior crest of an enfilading battery should be 
 nearly perpendicular fce the prolongation of the line to be en- 
 filaded; and be so placed that the shot from all the guns 
 shall sweep the terreplein throughout its entire length; The 
 position of a battery that will satisfy this last condition can he 
 readily found, as it must evidently lie within the angle, formed 
 by producing to the exterior the diagonals of the terreplein to 
 be swept. The best position of the guns will be to place one 
 so that its line of fire shall be nearly on the prolongation of 
 the interior crest of the line enfiladed, and the remainder on 
 that side of this one on which the exterior line of the terreplein 
 prolonged may fall. 
 
 29. ..In a counter-battery, the interior crest should be nearly 
 parallel to the line to be counter-battered. A position some- 
 what oblique to the line, so that the shot of the battery may 
 enter the embrasures obliquely, is also a good one for tearing 
 away the cheeks of the embrasures, and exposing the guns of 
 the defences. 
 
 30. ..Whenever a position has to be taken up for an enfilad- 
 ing or a counter-batterv, in which the .direction that can be 
 given to the interior crest is very oblique to that which it 
 ought to receive, it will be necessary to make the embrasures 
 of the battery with a corresponding obliquity to the direction 
 
ATTACK AND DEFENCE OP PEBKANEHT WORKS. 311 
 
 of the parapet; and, to avoid the inconvenience of these last, 
 it -will be farther necessary to break the interior crest Into an 
 indented line, to allow the muzzles of the gam to be run the 
 Requisite distance into the embrasures; placing one side of the 
 indent perpendicular to the axis of the embrasure, and the 
 other parallel to it. 
 
 &k. ..Enfilading and counter-batteries are usually armed with 
 18 and 24-pounders, and 8-inob howitzers. The fire of the 
 gttns is mainly directed to destroy the artillery of the di 
 that of the howitaera to sweep the eovered-ways and ditches, 
 to destroy the palisadings, and injure the traverses by the ex- 
 plosions of the shells that may lodge in them. A- a general 
 rule, there need not be more than seven piece-,, nor should 
 there usually be less than three in anyone battery; the num- 
 ber depending upon the bearing which the artillery of the 
 part to be silenced may have upon the ground on which the 
 works of the besiegers' must be placed. Tin- batteries should 
 he as far asunder as practicable, so as not to invite a coi 
 tration of the tire of the defences upon any point by the accu- 
 mulation of a large number of pieces on it, and thus multiply 
 the chances of loss both to the treops and ?//'//< 
 
 32. ..In computing tin- extent of front of a Lattery, PI. 11, 
 
 Fig. •-'''>. an allowance of 1"'. 1 alotlgthe LI 
 
 is made tor each piece, and <">' for each splinter-proof gabionade 
 
 traveive, one of which is placed between every two gun s, when 
 
 there are more than three in a battery. The flanks 
 
 guns are covered by an epaulment thrown up . or both 
 
 extremities of the parapet. The length of the epauln 
 
 measured along its interior crest, may he from 
 
 direction of the epaulun m with respect to the parapet will 
 
 depend on that of the lire of t'i. , ; il rule, 
 
 the interior <t< 91 of the epaulment shonl I 
 
 about 100° with that of the parapet. Wh 
 
 on the natural surface, the earth fof the parapet. < paulm 
 
 and tra\ 1 1 ditch in fro: | 
 
 epaulm< tits, and 1 ara A 
 
312 ATTACK AND DEFENCE OF PERMANENT WO I. 
 
 narrow ramp, at the end of eacli epsulment, leads from the 
 natural level to the bottom of the ditch, and serves for the 
 convenience of the men whilst throwing up the battery. A 
 trench, of the ordinary dimensions of an approach, and defiled 
 from dangerous points, leads from each extremity of the bat- 
 tery co the parallel in its rear. 
 
 33. ..If the embrasures are so oblique as to require an in- 
 dented parapet, the side or face of the indent, through which 
 the embrasure is pierced, should be 2:>', and perpendicular to 
 the axis of the embrasure. The other side, <>r flemk of the 
 indent, should be 25', and parallel to the axis; a distance of 
 only 7' being left between these two last lines, to give all the 
 thickness practicable to the portion of the merlon that forms 
 the outer angle of the indent ; for a like reason the face of the 
 indent, at the extremity of the battery, should extend 21' be- 
 yond the axis of the embrasure. These data will serve to esti- 
 mate the tofcil length of the parapet. Its thickness, estimated 
 from the inner angles of the indents, is 18'. 
 
 34.. .The profile of a battery will depend, both for its dimen- 
 sions and form, on the command of the point from which it 
 can be attained, and on the position of the surface of the 
 ground, on which it is laid out, with respect to the defene- 
 
 Where the site of the Battery is horizontal, and the com- 
 mand of the defences over it is within the usual limits of 20' 
 to 30', the following forms and dimensions, Fig. 27, will afford 
 ample cover to the men and materiel of the battery, when the 
 platforms are on a level with the natural surface : Height of 
 the interior crest, T 6". Thickness of parapet, 18'. Interior 
 slope, 4-1. Superior slope, 1-12. Exterior slope, the natural 
 slope of the earth. The same dimensions and forms may be 
 given to the epaulments, except the distance between their 
 interior and exterior crests, which may be reduced to 12' when 
 the direction of the epanl incut is quite oblique to that of the 
 fire of the defences. h\ the contrary case, this distance should 
 be 18'. The depth of the ditch is taken at 5'; its width will 
 
ATTACK ANT) DEFENCE OF PERMANENT WORKS. 813 
 
 be regulated by the quantity of earth to be furnished for com- 
 pleting all the parts of the battery. 
 
 35. ..The axes of the embrasures) Pigi 26, are I s ' apart, ex- 
 cept at tlic points where splinter-proof tra/verses are placed — 
 the requisite distance at these points being 24', allowing 0' for 
 the width of the base of the traverse. The sill of the embra* 
 sure is 3' 6" above the platform for guns mounted <>u tin-, ordin- 
 ary siege carriage.; its sole is parallel to the superior slope. 
 The mouth of the embrasure is of a trapezoidal form, being 
 2' wide at bottom and •">' at top. The splay of the sole is ob- 
 tained by giving the sides an inclination of 1-1" with the axis. 
 The top line of the cheek is obtained by setting off along the 
 direction of the exterior crest, from the point where the side of 
 the sole cuts it in projection, one-half the vertical distance be- 
 tween these two last lines, and joining the point thus found 
 With the exterior point of the mouth at top. 
 
 Embrasures of howitzers may receive a counter-slope, giv- 
 ing the sole nearly the same, inclination, from the sill upward, 
 a> the feast angle of elevation under which it may be required 
 to aim the pi< 
 
 B6.,.The parapet of the battery and the embrasures arc re- 
 vetted either with gabioas, fascines, or sand-bags, or with a coop- 
 binatioD of th 
 
 The epaulmenta need not be revetted, their interior si 
 being made as Bteep a- the earth will stand at. Ihe gabion 
 revetement- is the firmest and most durable. Wlien u-< <} far 
 the parapet, two tiers will be requisite. 
 
 The requisite slop< • o to the gabions of the 
 
 by placing a row of under them, alo« . 
 
 interior alopi >ther row of fi s laid on to] 
 
 tier, along tic interior slope, on which the gabioi 
 
 [uisite height 
 either by pla Is on the top ti«i- or by < arth alone. W 
 
 e used * laid in - 
 
 interior 
 
 4U 
 
314 ATTAi k A.vn DEFEftOB 0* im i:m\nv\t WoKKS. 
 
 imr joint. To give the bags greater durability, they should l>o 
 impregnated with tar before being filled. 
 
 It has been found that raw hides will preserve the rev< 
 ments of tin- cheeks from the effects of die concussion pro* 
 duqed by the firing, ror this purpose, the bide is folded with 
 the hair inward. It is confined to the top of the cheek by 
 pickets driven through it into the merlon; and at the month, 
 arid the other end of the check, by packets driven into the re- 
 vctement. The lower end is allowed to hang loose. 
 
 87.. .The splinter-^roof traverses'^ Fig. 2&, arc formed of two 
 tiers of gabions. He lower tier consists of two parallel rows of 
 eabions, and is .v wide at the base; the rows of gabions are 
 slightly inclined toward each other at top. The upper tier 
 also consists of two rows, which rest on two roWB of fascines, 
 laid on the first tier, the gahions leaning against each other at 
 top. The gabions and the space between them are well tilled 
 in with earth, which is heaped above the top tier. The tra- 
 v.t.-c may he from 15' to IS' long. A passage-war of 2' is left 
 hetween the parapet of the battery and the end of the traverse. 
 
 38. ..Thi' platforms are Itf 6" wide. 15' long in the (dear, and 
 receive an upward slope ot 7" to s" from thehurter to the tail. 
 They are composed of 6 keepers, each l.V long and 5" on the 
 ,idr : of L2 ].lanks, each lo'fi" long and 2" thick; of 2 ribands, 
 or side-rails^ of the dimensions of the sleepers; and of a lmr- 
 ter. The sleepers are firmly imbedded in the ground, and se- 
 cured by stout pickets at their ends. The planks are (damped 
 between the side-rails and outside sleepers, these pieces being 
 
 connected firmly either by screw-bolts and nuts or by rack- 
 lashings. 
 
 39... In sunken batteries, the same length of interior crest is 
 allowed for each guh as in the preceding case; but when the 
 battery requires splinter-proof traverses, an allowance of 86' is 
 made for the distance between the axes of the guns separated 
 bv a travel-si'. The position and length of the epanhnents arc 
 also determined as in the preceding case. 
 
 40. ..The trench of the battery, Fig. 29, when first excavated 
 
ATTACK AND DEFENCE OH PERMANENT WoUKS. 315 
 
 • 
 
 is ir>'4R-iilo at bottom, 3' deep in front, and 2' 6" deep in reard 
 The front Is cut down vertically in firm soil, and the revi 
 receives a Blope of A. [Die interior crest of the parapi 
 4' 6" above tie natural surface; the parapet* 1 8' thick) the 
 interior slope, 4-1 ; the exterior Blope, 1-1. A berm of t$" is 
 lot't between the parapet and the trench when first excavated. 
 
 •11. ..As the dimensions above given to the trench will fur- 
 nish earth only for the parapet, that required for the epanl- 
 ment is taken from a ditch 5! deep exterior to it: and a small 
 portion of ditch is made exterior to< the parapet, and opposite 
 the position of each splinter-prqpf traverse, to provide the 
 earth requisite for the traverse, and which is taken from tin' 
 trench.. The epaulment, if exposed only bo an oblique tire, 
 need not be thicker than L2'. 
 
 4:2. ..The embrasures receive the same form, dimensions, etc., 
 as in the precedii § 
 
 ■t-'!...The front of the trench is revetted with fascines. Xo 
 put up this revetement, the trench is widened by cutting av 
 the front, nearly to the width of the benn, and almost verti- 
 cally. Thi.> will admit the muzzles of the iznu> to he run well 
 into the embrasures. 
 
 T.i avoid the labor and exp . it has hcen 
 
 proposed neither to revet the portidn o/ the trench bord< 
 the epanlment, not the interior slope of the epaulment; hut to 
 ■ at this part, •"'' wide, when the trench 
 
 instruction, and. afterward, to L r ive both to this portion of 
 the trench and the interior of the epaulmeni 
 as the earth will stand well under. 
 
 44... When splinter-proof tra\ < r» - are i i of 
 
 the ground, <'»' wide on which the travert 
 The traverse is made by first placing two parallel ron 
 cines at .V apart, on which a tier of gabioi 
 
 touch a' 
 is tilled in the gabions and tl 
 keajfi d up i 
 
 Tin 
 
316 ATTAi K AM' MM. N.I 09 ITKMAMM WoKK>. 
 
 able slope, and revetted with fascines. A passage of _'■% left 
 
 between the gabionade of tin- traverse and the interior slope 
 of the parapet. 
 
 45. ..To provide against rainy weather, two of more holes 
 should be dog at Buch point* of the trench of the battery m 
 may be found most convenient to receive the water that col- 
 lects in tin- trench; and precautions should be taken to pre- 
 vent water from being received into the trench, either through 
 the trenches leading to it or from the natural surfac. 
 
 4<'>...Tlie powder magazines shctuld be at least 3o' in rear of 
 the parapet <>f the batter.^. The ceiling of the magazine 
 should not he more than a few inches above the natural level. 
 The interior height need not be more than .V. The width may 
 be G', and the length 12', in the clear. The sides ot the maga- 
 zine may he formed of frames ami sheeting boards; or of a 
 row of gabions crowned with two courses of fascines. The 
 magazine is covered at top by splinter-proof timbers, f."xl'", 
 laid in juxtaposition, and covered with at least 3' of earth, 
 both on top and on the .-.ides toward the parapet. A passage 
 lend- into the magazine, on the aide from the parapet, which is 
 reached by one or two inclined trenches. 
 
 4VT..vMoETAB Haiti kiks. There are two kinds of mortar 
 batteries used in the attack: those lor mortars throwing >hells, 
 and those for mortars throwing baskets of stones, or other like 
 projectiles. Besides these, there is theCoehorn mortar, which, 
 from its small size, mav he placed in any nnobcupied corner 
 of the trenches. The first kind of batteries may hi' in front of 
 the first and second parallels, or on any other points farther 
 back. The positions ehoeen.fbr them should he mch as to 
 
 bring as greal a portion of the defences under the direction of 
 their lire as practicable, to increase the chancer of destructi- 
 
 bility of each shell thrown. The secood kind are placed in 
 front of the third parallel, mainly with a view to annoy the 
 covered-ways and parts adjacent. 
 
 4S...The platforms of these batteries may be laid on the* nat- 
 ural surface, in which case, the same forms and dimensions 
 
ATTACK ami DEFENCE 09 I'IKMWim W6JRKS. 81T 
 
 will bo given to the parapel and epaulmento of the battery 
 in gun batteries; but as the mortars must be set back from the 
 parapet, to enable the shell to clear the interior crest by about 
 
 3', a lWeteinelit will Hot lie nece.->;^-y. and tlie | .:ir:i| >et may 
 
 ei oeive as great an interior slope at the earth can be made to 
 stand under firmly. 
 
 ■1!'.. .The front of a mortar battery is estimated by allowing 
 15' for eaeli mortar, and <;' for each splinter-proof traverse. 
 
 Those batteries are, however, usually sunk' below the natu- 
 ral surf, several feet difference of level in the position* 
 
 of a mortar will have hut little etlect on the range or the tra- 
 jectory. The profile suitable tor such positions, under ordinary 
 eircumsl - the following: Width of treach at bottom, 
 
 13' »i". Depth in front 8' «i". Depth in rear. f. Reserve 
 slope, h. Front slope. W bate. If ight of parapet, 41. Thick- 
 m m of parapet^ l v '. Berm, 1'. 
 
 60... The earth tor tlie epaulment is taken from ai 
 ditch ; and. when splinter-proof traversi - are required, por- 
 tions of ditches are made oppoBiu \-> their position, to furnish 
 the requisite earth. 
 
 51...The platforms of mortars are T 6" long by & 6" wide. 
 jThoy are composed of two ground-sills, T '">" long and *;" 
 squ ion- and »''" sqoai 
 
 long and 4" square; 8 planks, each 6' <T long and 4'* thick. 
 The ground-siUs are laid horizontally, and firmly embedded in 
 the ground at 4' 6" apart, and transversely to the - 
 
 1 ]>on these the - confined by I 
 
 i ml. The plank I the 
 
 pen mi 1 gun plat 
 
 ■ 'J... I '.i. i ' ■ I .\poM d ] . - 1, 
 
 breached by heavy gui 
 
 and batter* B thrown up iii sud 
 
 tho- 
 
 the breach 1 
 
 I 
 
318 ATTACK AND 1 >!■:!■ l M K 09 I'lKMAMM \\oi;k>. 
 
 fences, at points where no obstruction will intervene to p 
 vent the fire of the guns from being directed at a point of the 
 wall to be opened low enough to form a breach practicable to 
 the ascent of an assaulting column 
 
 In either of the tatter cases the batteries must he sunk: the 
 level chosen for the platforms being such as to subserve the 
 object in view. The embrasures in these cases are usually cut 
 out of the parapet, as an ordinary, trench has generally to he 
 first established as a preparatory step to commencing the bat- 
 tery* The forms and dimensions adopted for other sunken 
 batteries will apply to these cases, with such modifications as 
 may be demanded by, the site of the battery, and the position 
 of the point to he attained by the fire. 
 
 When a hreach battery Is established either on the glacis 
 or upon the terrcplein of a work, its guns will generally he 
 exposed, both on their flank and rear, to the lire of dangerous 
 commanding points, from which it will he necessary to cover 
 them by traverses. The number of traverses and their posi- 
 tion will depend upon the command and position of the dan- 
 gerous points. To cover from the flank fire, if the command 
 of the dangerous point is considerable, like that of a cavalier 
 retrenchment, it may be necessary to place a traverse betweed 
 every two nuns, or even between each. The traverses used in 
 such cases receive a thickness of 14', or seven gabions, like 
 those for covering an ordinary trench from as entilading lire ; 
 their length will depend upon the relative positions of the 
 dangerous point, and the exterior point of the battery to be 
 covered ; their height is usually not greater than the traverses 
 for a trench. m 
 
 When the reverse of the battery is exposed, it will generally 
 arise from the salient position of some comparatively distant 
 point, from which a slant fire* may he brought to hear on this 
 part of the battery ; in which case it will generally he easy to 
 cover the part exposed by running out, from the reverse of the 
 battery, an end of trench, to form a wing traverse that shall 
 intersect the lines of fire of the point upon every part exposed. 
 
ATTACK A\P DEFENCE 01 l'lKM.wiNT WOBK0. 319 
 
 54.. .The nuns, of breach batteries should bo so placed that 
 the direction of their fire may be as nearly perpendicular m 
 practicable to the line of wail to be breached ; and where 
 these lines are oblique to Bach other, the obliquity should Dot 
 exceed 4f>°, otherwise the effect of the shot will be greatly di- 
 minished, -and the operation retarded. 
 
 Besides the breach batteries, it will »be necessary bo place 
 counter-batteriea on the glacis. Their object will be to conn* 
 tor-l>atter and silence tlie artillery of those portions of tlio de- 
 fences which can be brought to bear on the broach4)atterie&, 
 or on the passages of the ditehea. These batteries will netialty 
 be placed on the prolongation of the ditches of the deferti 
 Tlieir arranireiin mt will be, in all respects, the same as that of 
 the breach batti ri 
 
 SIEGE <)Pi;k.\tk»\s. 
 
 55...The operations of a siege are usually divided into three 
 epochs. In the first are comprised the investment, and other 
 operations, preliminary to breaking ground against the work) 
 or opening the trenches. T od comprises the labors 
 
 from the opening of the trenches to the completion of the 
 third parallel. The third, the subsequent operations to the tar 
 faction of tin' work. 
 
 Fmsi P] !•; 
 
 i mim. This ii the fir-t acttve operation of the 
 
 1m sieging foi >bject being to cut off all communicnl 
 
 bet'-' garrison and the 
 
 y kind from being 1 • the work. ' 
 
 ything in its vicinity that might in any 1 
 ble to th< >U, and. finally, t 
 
 of the defence 
 
 For tii' 11I attainmei I 
 
 force, which is mainly, if 1 
 should move Upon the work with c< 
 
320 ATTACK AND DEFENCE OF PERMANENT WoKK<. 
 
 .iftor surrounding and Btecaring all avenue- to it, should send 
 
 (Hit detachments to scour the environs no ti) the Very gates of 
 
 the work, if practicable. an<l bring off with them, or destroy, 
 all persons, cattle, provisions, etc., met with. A chain of posts 
 and sentinels is in the meantime established in the best | 
 
 lions to prevent all ROCeSfl to the work or egress from it; cafe 
 being taken to seled for the post points which are not ex- 
 posed bo the artillery of the work, or are beyond its range* 
 The posts occupied by the troops during the day time, and 
 termed the </iiihj <-i>nh>n, are shitted at dark, and points nearer 
 the work are taken np. to form the nightly <-<>r<I<m< ami hem it 
 in more closely. The posts and sentinels for this purpose 
 should be pushed as far forward as they can find shelters from 
 the musketry of the defences; and under their protection the 
 reconnoitcring officers should spare no efforts to gain an exact 
 idea of all the ground exterior to the work, and of the char- 
 acter of the defences. 
 
 57. ..Posting Besieging Force. The main body of the be- 
 sieging army, with the engineer and artillery siege-trains fol- 
 lows closely upon the investing corps, to prevent the line taken 
 up by the latter, which, from its extent, is necessarily weak, 
 from being forced either by the garrison or by strong detach- 
 ments from without. The positions for the camps of the various 
 corps are designated by the commanding general, after a care- 
 ful reconnoissance. These are placed beyond the range of the 
 heavy artillery of the work, with their color fronts facing from 
 the work, and, as far as practicable, on points favorable to the 
 health and comfort of the troops, and the defence. Whenever 
 natural obstacles occur between tin: camps, they must be 
 crossed by good lines of communication, so that no impedi- 
 ment may be offered to the speedy concentration of the troops 
 upon any point threatened from without. 
 
 Besides the positions taken up for the camps, the besieging 
 force will also occupy all points exterior to the camps, within 
 cannon range, by which they are commanded, securing them 
 
ATTACK AX1) IlKFKM I' Of l'i:i;MA\'\l WOBKS, 321 
 
 by field-works of sufficient strength to Bubserre the eud in 
 view. 
 
 58. ..In i 1:1 \« iimknis of Damps* 'the front and the rear of 
 i camps are also secured by lines of field-works. The exterior 
 works, termed the A///- of C&rcwnvallatum, should fornJ an 
 Unbroken line of intrencliments, composed of the most simple 
 elementary parts, as tenailles, redans, etc., with a slight pro- 
 file; its ehtef object behig'to prevent sncc nail detach- 
 ments from slipping into the place. The interior line, 
 the /.''/' of Ckfunfamattatioto) is composed of detached works. 
 which, if the garrison is strong, should be in defensive relation's*. 
 The main points which shottkj be occupied o-y the! . are 
 the principal avenues to the defences, and the p 
 for the parka of the siege train, to Becure these points from the 
 
 attempts of the garrison* and to reA4er the entrai f lai 
 
 convoys into the defences impracticab 
 These lines are placed about 200 yards id front and rear of 
 
 the camps. 
 
 59. .'.In the later sieges in Europe, lines of circumvallation 
 particularly, were seldom resorted t«»: the btesi ateriting 
 
 themselves TOth occupying only the main points of their ; 
 tion by field-Works, and giving tin- intervening space such 
 
 nld be afforded bj strong patrols and posts. This 
 departure Prom former practic . in most From tho 
 
 want of strength of the besieging force, anii ntly 
 
 attended by the vi-v events against which lines are chi 
 effectual in guarding. Aa a field of battf < 
 force Of sufficient strength to cope with tfa ing artni 
 
 tion taken behind a line of circuravallation is, but 
 ligible — a maxim that applies t<. all i 
 -\\-<':d; ! in. - : and in almost everj 
 has been made igai -' ich ; 
 and has i heavy his* on th< 
 
 '-, let t! 
 oj-e'ii to this obj< 
 able f<«r tip 
 41 
 
322 ATTACK AM' DJUXNUJI OT 11 KMANINl WoKK-. 
 
 they ought to be thrown up in nil cases when' the moans of 
 tlie best will admit of it. 
 
 $0i..PBBPA&ATl!ON8 l"i: OPEBOfTG Till TsSNCHXB. "Whilst the 
 
 besieging force is occupied in arranging and securing their , 
 camps, a portion of it is employed in preparing the trench 
 material.-, establishing the parks, and getting everything in 
 order preparatory to breaking ground against the defence 
 At the Bame time, close reconnoissances ami careful instru- 
 mental surveys are made by i&e staff corps, to obtain <hitii for a 
 map of the defences and their environs, with a view of draw- 
 ing up a plan of attack. "With this object, the bearing and 
 prolongations of the fates an4 capitals of all the defences 
 should he carefully laid down; the character of the defences 
 on every assailable point noted ; that of the parts bearing on 
 these points, and the nature of the ground over which they 
 must be approached. 
 
 Gl...Thc parks, magazines of powder, and other depSis^ are 
 placed on the most secure points, beyond the range of the 
 heavy artillery of the defences, and, If practicable, should be 
 hidden from their view. The points selected, if not in the im- 
 mediate neighborhood of the ground on which itjs decided to 
 open the trenches, should have avenues of easy access to it, for 
 the transportation of whatever may be requisite in carrying 
 forward the works of attack. 
 
 62. ..Point of Attack. After obtaining all the information 
 that can be had from the reconnoissances, surveys and other 
 sources, the next object is to decide upon the portion of the 
 defences 'which it will be necessary to gain possession of to 
 force the garrison to surrender ; this portion, usually embrac- 
 ing one or more fronts of the enceinte, with their outworks, 
 and any advanced works that may be- connected with them, 
 and must be reduced before they can be assailed, is termed the 
 J'o'mt of Attack. It is in the choice of this point — a decision 
 which mainly rests with the commanding officer of the engi- 
 neers — that the judgment and skill of this officer are shown. 
 In making this selection, *he must carefully weigh, not only the 
 
ATTACK AND DEFENCE OP PERMANENT WOBKS. 328 
 
 relative strength of the various points of the defences which 
 arc accessible, hut the character of the site apon which the 
 trenches and other works of the attack most be lai<l out, and 
 Che facilities of an easy communication between the park.-, <h- 
 pdts, etc., and the point selected. 
 
 63. ..In considering the strength of the defences, thoee parts 
 arc regarded as unassailable by the ordinary measures of ad 
 attack, which border anon precipices, marshes, fi watei>cou 
 that cannot be forded, or arc protected by works on inacd 
 hie points, the fire from which swops in flank and reverse the 
 ground over which the trenches must be run. Those p 
 again, are considered as offering peculiar difficulties which 
 present a -eric- of works, in good defensive relation-, which 
 can only be earned in succession; or which arc mine.]; or 
 which have their ditches arranged for ■ play of water; or 
 which have dry ditches of unusual depth; otV finally, where 
 the work.- to be carried arc displayed on a right line, embrac- 
 ing the same extent of front that the 1" can take up 
 with their trenches. The bointa which are becked upoi 
 most advantageous to tin- attack are those in which the general 
 combination of the works foru nt point with respecfto 
 the rot of the defence bat 
 little support from the collateral portions; can be enveloped 
 l»v a line of trench of much great r i stent than itself, a 
 which positions can 1 btained i'<<r enfilading and other bat- 
 teries, the fire of which will 'it upon that 
 defei 
 
 <il....\- regards tie n which I • and ol 
 
 works nm.-t he Laid out, the diflicoltu 
 straction by hare rock, marsh, or hard, si 
 readily appn »ver can only be had on I 
 
 by bringing the earth from a ' te para] 
 
 dik- md <»n the la- 
 
 the trenches, and the add I l 
 
 troops from the Ira 
 by the shot ol tin 
 
3l'4- attack \m» defence of permanent works. 
 
 are others less obvious which should be taken advantage of or 
 be avoided, as favprable or otherwise to»the construction of 
 the work* of the attack. A surface, for example, which slopes 
 or falls away toward the defences, if commanded by them, is 
 unfavorable both to the construction of trenches and batteries; 
 fee, "to gain sufficient cover, both the parapet and trench will 
 have to receive dimensions greater than under ordinarj cir- 
 cumstances; and the defilement of approaches will also be 
 easily effected. A surface which rises toward the defenc< 
 verv favorable, both for gaining cover speedily and for defiling 
 with advantage the approaches; but is less so as a site for bat- 
 teries if the slope is rapid. An undulating surface may offer, 
 in some points, natural covers, and be at other points favorable 
 as sites for batteries ; this will depend upon the position ot the 
 undulation of the surface with respect to the lire of the de- 
 fences. A ridge, for example, leading out from the defences, 
 whilst it would present a cover to the works on one side of it 
 from the fire of the defences on the other, would expose the 
 trenches on the other side of it to a plunging fire from the 
 same points. 
 
 'A narrow valley, similarly placed, would he verv unfavor- 
 able, as both of its sides would be exposed to a plunging lire. 
 
 Seconh and Tm in) Periods. 
 
 65...Plan ami Journal <>f the Attack. The plan of the 
 attach is necessarily based upon the character of the defences 
 of the point of attack, and of the site upon which the ap- 
 proaches and other works of the besiegers must be laid out; 
 and by this term is understood both the means to he used at 
 the successive stages of the operations, and the disposition 
 given to the trenches and other works. The journal of the 
 attack is a record of th% daily operations of the besiegers; and 
 is also a method in use among engineers to estimate the dura- 
 tion of a siege, from the opening of the trenches to the reduc- 
 tion of the work, on the supposition that the works of the 
 attack can be Carried on regularly, without interruption from 
 
ATTACK AND DEFENCE OB IM.KM \ \ l\T VfOQBB, 325 
 
 unforeseen contingencies: a method of . valuation which, as it is 
 based on the time required to construct a given amount of 
 work. a> determined both from data furnished by actual b!< 
 and the results of experiment in schools of practice, may be 
 relied on as an approximation as elose as the case admits; and, 
 when applied in a spirit of fairness, may senre il B leaf of the 
 comparative strength of different combinations or systems of 
 permanent works. 
 
 66.. .The general disposition of the works,, of the I rs is 
 
 laid d<»wn on the map. made of the defences and envil 
 with ae i i-'.i<\ as ean be insured by survey- carefully 
 
 made; and, from the results obtained in this way, the offi 
 charged with this duty are enabled to set out on the ground 
 the necessary points by which those charged with directing 
 the construction of the works are guid* d. 
 
 • ;7....\> an illustration of the plan and journal of attack. We 
 shall suppose the point af attack selected, PL l_. Fig. 1, 
 to be an acute bastion With the two adjacent demilunes; and 
 that the only collateral works, the fire of which bi art on the 
 
 ground over which the trenches must be run, are two* coll) 
 
 al, obtuse bastions, the faces of which cannot be enfll* 
 owing to their prolongations falling within the salient 
 adjacent demilunes, and the two collateral demilunes ; making 
 in all one bastion and two demilunes, with tJieii dent 
 
 outworks, which must he entered by breach oi otherwise] and 
 two bastions and two demilunes, with their dependent 
 the tire of which must be kept under. 
 
 ' - : aches will be pushed forv I ion 
 
 of the capitals of the thn • 
 
 parallels will embrace a sufficient front to incJ prolon- 
 
 gations of tie ;' all tie 
 
 inst which enfilading l»at 
 ■ ..The first parallel will bi 
 
 OlOSt a'i |]|< 1 
 
 nearly to the lin< 
 
 which lead from it to th< 
 
326 ATTACK AND I>1"1 1 N» B OP ITKMAM NT WORKS. 
 
 zig-zags across the capitals, each not over 100 yards in length, 
 and defiled from the most dangerous points within cannon 
 range. 
 
 7"... I'ii:-t NlGHT, The position of the portion of the trenches 
 apon which tlie besiegers are to break ground having been 
 laid <>ut. and the materials for the wyrk having been placed in 
 order for distribution, so as to avoid all unnecessary delay and 
 
 contusion, the workmen arc assembled at the depots of the 
 trenches before night-fall to receive their Implements. The 
 men selected for this duty are troops of the line, who usually 
 take their arms with them. The men are divided into work- 
 ing parties, each of which is under the command of an office* 1 
 of the line, and they are marched in single file by a Hank and 
 posted, after night-fall, where they are to work under the di- 
 tion of the engineers. 
 
 The portion of the trenches opened this night are, usually, 
 only the approaches that lead from the depots of the trenches 
 to the first parallel, and that portion of this parallel which em- 
 braces the capitals of the point of attack. To guard the work- 
 men from sorties, as many battalions of the line as may he 
 requisite, termed thegiwzrds <>fl/i< trenches^ are thrown forward 
 about 30 paces in advance of and on the Hanks of the men who 
 open the first parallel. The ilank companies of these batta- 
 lions, divided into sections, cover the front of the battalions, 
 and are posted about 30 paces from them; and each section 
 posts two sentinels at about the same distance to its front. The 
 sentinels keep a look out, kneeling on on.- knee ; the remainder 
 of the troops lie flat on the ground to avoid the lire of the de- 
 fences. 
 
 When the working parties are all posted, the men of each 
 lying flat until all are ready to commence the work, the order 
 is given to rise, ground their arms a few paces to the rear, and 
 break ground. 
 
 The guards of the trenches keep their position until near 
 dawn, when they are withdrawn and take post in the parallel, 
 which, by this time, will be nearly excavated to its full width. 
 
ATTACK AND DEFENCE! OF PJ i:\IA\l XT WoIiKS. 327 
 
 On the succeeding day all that remain.- to be done to the 
 trenches opened is completed, and everything is gol in readi- 
 ness for the work of the coming night, 
 
 71...Si « mm. Night. The parallel will be extended this night 
 to embrace the prolongations of all the laces to be enfiladed, 
 and some 100 or 150 yards beyond the extreme points so <1«- 
 lermined. A large square redoubt will be constructed at each 
 
 extremity of the parallel, which will be armed \\\\} ] field 
 
 pieces; and an epaulment for cavalry will be thrown hp in the. 
 rear of each redoubt i the object of these works being to con- 
 tain troops to act against sorties made on the flanks of the par- 
 allel 
 
 The zig-zag approaches are pushed about 160 yards in ad- 
 vance of the parallel. The positions of these approaches are 
 determined on the plan by setting off points cm the first paral- 
 lel at 80 yards on each side of the capital, and drawing I 
 from each of these points to corresponding point! about 15 
 yards on the side of the capital, at the salieni of the covered' 
 way. then limiting the length of each zig-zag ofthi », the 
 
 direction of each depending on its defilement. To cover more 
 completely the rev< fee of each zig-zag, and secure it from i 
 
 tinii.- that mi^ht be taken up. e\teri..rt<. the defei • nli- 
 
 lade it. the zig-zag in advance should be prolonged back 
 
 beyond the limiting lines a d ■ :' LO or 12 yard- to 
 
 rear of the one immediately behind. 
 
 72.. .R] m\kk. It maj rved here that by running ap> 
 
 proaches upon three capitals, we not only multiply the lin< 
 communication between the parallels, but divide the attention 
 of the b< The lines of the capitals are also the i 
 
 suitable for ' (junta : first, * 
 
 the short* st n the parallels and t! 
 
 within 
 the angle formed by the prolong] 
 
 re of tii. 
 oft) 
 
328 ATTACK AND DHFKNc:' OF IT.KM AN'I'NT WORKS. 
 
 tliis position the approaches arc nmre easily defiled from the 
 collateral fire than in any other. 
 
 By confining the zig-zags within the lines drawn from the 
 parallel, and converging toward the salients, the front 6i each 
 approach is gradually eontraeied as it nears the salient, and 
 offers less obstruction to the fire of the parallel. 
 
 73. ..The trenches and other works left incomplete at the end 
 of the second night are finished on the following day; and 
 this rule is followed throughout, as the trenches Commenced 
 by night are generally in a suitable state by dawn t<> give 
 cover to the workmen and troops', and can be occupied, and 
 what remains to be done to them be completed in safety by 
 day. 
 
 74. ..Third Night. The approaches are pushed forward 275 
 yards from the first parallel, and here the second parallel is 
 commenced; a small portion of it only on each side of the ap- 
 proaches being opened, in which to lodge a few troops for the 
 protection of the workmen. 
 
 This parallel is of less extent than the first, embracing only 
 the prolongations of the faces of the point of attack. It is 
 usually connected with the. first parallel by a defiled line of 
 trench at each of its extremities. Its distance from the first 
 is determined from the consideration that the workmen em- 
 ployed on it must be protected by the guards of the trenches, 
 who are still stationed in the first, and who, to afford this pro- 
 tection, should be posted where they can come to the aid of 
 the workmen before the garrison can reach them in a sortie. 
 
 The rule here observed is also a general one. The trenches 
 under construction never in any case being advanced so far 
 that the guards in their rear cannot come up to their support 
 before they can be reached by a sortie from the defences. 
 
 75. ..Fourth Night. The second parallel is entirely laid out 
 on this night, and is completed on the following day. The 
 guard of the trenches takes post in the parallel as fast as a 
 part of it is finished; a reserve equal to about one-third of the 
 whole being left in the first parallel. 
 
ATTACK AND DKFK.Wi; OF I'KKMAM.M WOKSBk 829 
 
 As the second parallel is at 325 yards from the salient of the 
 place,' the workmen arc much eiposed to the fin of grape 
 shut: it will, therefore, be necessary to use the flying >a]» in 
 its construction. 
 
 7<;...I''i![ii ami Sixth Nights. Thus far the works of the 
 attack have been pushed forward without the aid of artillery, 
 but beyond the Becond parallel the fire of the defences 1m- 
 comes so destructive that farther progress cannot be made, 
 without great sacrifice of life, until it is silenced. To effect 
 tins, enfilading, mortar and counter-batteries are plaeed about 
 30 yards in front of the parallel. The number of gun* in each 
 battery will depend on the importance of the face to be 
 silenced, and, according to tin's rule, the following distribution 
 will be made : ' 
 
 A battery of 8 pieces will be erected against each face of the 
 bastion of attack. A battery of 5 pieces againBt tin- right 
 tare of the demilune of attack and it.- covered-way, and one of 
 7 pieces against the left fao the fire from the Latter 
 
 bean more directly on the approaches than that of the, right 
 face. A.- the two collateral bastions arc supposed t<> be so 
 obtuse that their feces cannot be enfiladed, it will be necessary 
 to silence their fire by counter-batteries. As the left face 
 alone of the bastion, on the right of the one of attack, b« 
 direct action on the approaches, a counter-battery of •' 
 is erected against it. and so placed as to obtain a slant 
 into its embrasures. With regard to the collateral demilune 
 on the same side, as its right face has but a slight bearing on 
 the approaches, a batters of '■'< < 
 from being occupied l>y the I 
 its lj t, it will De 
 
 battery of 5 pi< battery i in 
 
 1r«.nt of the first parallel. Two or thr< part 
 
 h battery, t and dit< 
 
 The ne. nar batteries are plac< d in posit 
 be most effective, which i.- usuallj 
 capitals of tl 
 
330 ATTACK AND DEFENCE OF PERMANENT WOKKS. 
 
 t:u> arc placid in eaoh battery, an allowance of 8 mortars 
 being made for each front embraced by the trenches. 
 
 The mortar and gun batteries, the fire of which is not ob- 
 Btructed by the trenches in front of them, are snnk. The plat- 
 forms of-the others are on the natural surface of the ground. 
 
 Besides these Latteries, which will he completed on the tilth 
 and sixth nights, two or three zig-zags are pushed forward in 
 advance of the parallel on the same nights, if the lire of the 
 besieged is not too destructive. 
 
 77. ..Si \ i. viii Nl&HT. As the enfilading batteries will he 
 Completed and armed on the sixth night, on the following 
 morning they will all open their fire at the same moment, and 
 by night the lire of the place will he nearly, it' not entirely, 
 silenced." The approaches are then pushed forward, and demi- 
 parallels are established at from 100 to 150 yards in front of 
 the second parallel. The demi-parallels may be from 100 to 
 200 yards in length, and have a return of 25 yards at their 
 extremities to cover them on the flank. The length of the 
 demi-parallel should he so regulated as not to obstruct the fire 
 of the ricochet batteries. In some cases howitzers are placed 
 in batteries established at the extremities of the demi-parallels, 
 to enfilade the covered-ways; but as the demi-parallels are 
 within good musket range of the covered-ways, it will gener- 
 ally he better to arm them with infantry, the top of their para* 
 pet being arranged with loop-holes made with sand-hags, to 
 cover the marksmen whilst in the act of firing. 
 
 78...Ei(.inu Niuiit. On this night the approaches are pushed 
 forward by the Hying and full sap, as opportunity may offer, 
 and a portion of the third parallel is commenced when the ap- 
 proaches are within 0<> yards of the most advanced salients. 
 
 79...i\i.vni Night. The third parallel is completed. It 
 should present a less development than the second, so as to 
 be flanked by it, and will, therefore, usually embrace only the 
 salients of the point of attack. Owing to this, and its having 
 to receive the main body of the guard — the second parallel 
 now containing only the reserve, whilst the first is used only 
 
ATTACK AND Mil \. E OF PERMANENT WOBM. 331 
 
 as a depot for the materials and to receive the wounded — the 
 third parallel is made two ox three feet wider than the other 
 two. 
 
 S0...U1 m akk. With the completion of this parallel begins 
 the third and last period of. the attack. At this point, the 
 works of the besiegers are necessarily contracted to a very 
 narrow front, and present but little more development than 
 that of the point of attack: They are now upoii the immediate 
 
 gVOnnd of the defences, and within range of every mean- of 
 annoyance. In pushing forward from this position the besi 
 era are. to a great decree, deprived of the assistance that they 
 hitherto had from their enfilading and other hat: the 
 
 position of their trenches on the glacis musl obstruct this fire; 
 they can no longer use the Big-cag approach, hnt I gain 
 
 ground by the doable sap. and soon find themselves^ as their 
 works advance toward the re-euterings, the enveloped instead 
 of the enveloping party, and liable at every moment to have 
 their sappers cut off, and their labor! Btopped by sorties in 
 small parties. It is at this stage, then, that more than ordinary 
 precautions are requisite, not only to prevent retardation of the 
 works, but to avoid unnecessary sacrifice of life; by preparing 
 all possible mean- for insuring the sue I p. and 
 
 by not advancing on one until the last taken is perfectly secure. 
 BL..Tcm Nnon. A- the third parallel, PL 12, Fig. 1. 
 from it- position on tl -. will mi 
 
 (diet batt ■ /■'. it will he i 
 
 establish new ball n front of it. to dislodge the besi< _ r -'d 
 
 from this outwork. For this pur] 
 are found very sffectn e. These b l about 
 
 90 yard- in trout of the parallel, and 
 
 4 or 6 mortar- i- placed on ea in 
 
 the prolonged direction of 1 
 
 will he ready to C 'li the C 
 
 the morning 
 completion of tie third 
 
ATTAf K AND DEFENCE OF PERMANENT WOBKS. 
 
 crowning the covered-way; either by storm <>r by gradual ap- 
 proaches. In tin* former case, portions of the parallel arc ar- 
 ranged with steps to enable infantry to sally from it on the 
 covered ways. The sappers, with all the w cessary materials 
 for crowning the covered-Way, arc collected in the parallel. 
 At a preconcerted signal, a lire will be opened from the stone- 
 mortar batteries, ami all others that arc still effective, against 
 the covered-way and the other outworks. When it is per- 
 ceived that tin- fire has produced its effect in clearing the out- 
 works, at a preconcerted signal it will also cease ; the troops 
 will sally forth and carry the covered-way with the bayonet, 
 and, after gaining possession of it, they will shelter themselves 
 as best they can behind the. traverse from the tire of the be- 
 sieged. ^Whilst thev, in this way, maintain possession of the 
 covered-way, the sappers, who follow immediately in their 
 rear, will open a trench about 4 or 5 yards from the crest of 
 the glacis, around the salient place of arms, as tar as its two 
 traverses; when this trench will afford a shelter to the troops, 
 they retire from the covered-way into it. This trench is after- 
 wards connected by suitable communications with the third, 
 parallel. 
 
 From the circumstances under which this operation is car- 
 ried on, the probabilities are against its success and in favor of 
 a great sacritice of life in the attempt, if the besieged offer a 
 vigorous resistance and make a skilful use of the means still at 
 their disposal. With such chances, therefore, of failure, and 
 the certainty pf great losses even if successful, this mode of 
 attack should only be resorted to in some contingency where 
 the success of the siege depends on the time saved by it. 
 
 83... fa. i \ i viii NlQHT. When the covered-way is to be 
 crowned by regular approaches, a constant lire is kept up from 
 the stone-mortar batteries so as to render it untenable for more 
 than a very few men, A trench, termed the oirotdew place of 
 arms, is now formed, by starting from two points of the paral- 
 lel at 30 yards on each side of the capital, and pushing two 
 I tranches of full sap to unite at about 15 yards from the paral- 
 
ATTACK AND DEFENC1 01 l'l KMA NKM Woi, 
 
 lei, on the capital. From this point a doable sap is poshed 
 along the capital, to within 80 yards of the clients ol the dem- 
 ilune coveredrways. As the bastion covered-wa^ is very he- 
 tired, nothing more is done than to form the circular place of 
 anus before it. 
 
 84...Twi i. iin Night. The trench cavaliers before the demi- 
 lune salients arc commenced, and the sap Lb pushed forward a 
 few yards on the bastion covered-way. 
 
 85...Tmi:i r.i vin Nimm. The trench cavaliers, which require 
 from 36 to 48 hours for their completion, will be finished on 
 this night, and an approach pushed from the stone-mortar bat- 
 teries toward the reentering place of arms. 
 
 80...F<«rini i n in Xionr. The besieged being now driven 
 from the covered-wayi by the fire* of the trench cavaliers, :i 
 double sap is pushed toward the salient of the demilnne < 
 ered-way from the two extremities of the circular trench con- 
 necting the trfeoch cavaliers. Thesis two saps unite at 1 ■ 
 yards firom the crest of the glacis. 
 
 The approaches toward the reentering place of arms are ad- 
 vanced farther on. 
 
 - 7 ... I 1 1 1 1 1 vi ii N toHTi Hie demilnne covered-way is crowned 
 Ear as the leebnd traverse. The approaches on the reenter- 
 mg- place of .-inns and the salient of the bastion covered-way 
 ire advanced. 
 
 - ...A fourth parallel is began on this night, c 
 opposite the first traV< rses of the demilune eov< red-ways, and 
 uniting the approacl d toward the r< Sntering i 
 
 arms. 
 
 v '.'...Si\m i mii Ni'.in. The breach and cuunter-1 tl 
 around the salient pis demilni 
 
 and armed. 
 
 From 1 to 5 guns will be placi d on each branch of • 
 of the salient place of arms, in the j,, 
 lune ditch, to count, r-batter the port 
 which hear upon this ditch and t 
 
 this tire troiu retard;;..' Hie lodgn 
 
334: ATTACK AND DEFENCE OF PKHMANKNT "WORKS. 
 
 tcrreplein of the salient place of arms and the passage of the 
 •litch. About 4 guns are placed in a battery between the first 
 and second traverses, to open a breach in the left face of the 
 
 demilune. This breach should be from 20 to 3<> yards in width, 
 and not extend farther toward the salient than the position of 
 the pancoupe, so as to expose as great an extent of the interior 
 of the demilune as practicable. 
 
 The guns in these batteries will require cover in flank from 
 the faces of the bastions and their cavaliers ; and in rear from 
 the most advanced salients of the works still occupied by the 
 besieged, 
 
 The descent into the demilune covered-way, commenced on 
 the fifteenth night, behind the. first traverse, is finished; and 
 the fourth parallel is completed. The width of the fourth par- 
 allel is the same as an ordinary approach, owing to the diffi- 
 culty of defiling it. 
 
 These batteries will be completed and armed in 24 hours 
 after the crowning is commenced. The breach will be prac- 
 ticable in 12 or 15 hours after the tire is opened. 
 
 0O...Seventeenth Xk.iit. The approaches from the fourth 
 parallel are pushed forward on the salients of the bastion cov- 
 ered-way and the reentering place of arms. The crowning of 
 the demilune covered-way is gradually advanced and a lodg- 
 ment is made on the terreplein of the demilune salient place of 
 arms, from which the demilune ditch can be swept by mus- 
 ketry. 
 
 The descent into the demilune ditch is commenced on this 
 night, behind the traverse of the salient place of arms. 
 
 ( Jl...In advancing the sap on the different salients of the 
 covered-way, from the fourth parallel, care should be taken not 
 to push forward one faster than the others, so as not to oiler a 
 temptation to the besieged to sally out on the head of the most 
 advanced, to cut oil' the sappers. Moreover, the different 
 brigades of sappers should be protected by a few picked men, 
 stationed in short trenches that ilank the direction of the 
 double sap as it is pushed forward on the salients. 
 
ATTACK AND DEFENCE OF PERMANENT Woi:k>. 335 
 
 92. ..If, owing to the great width of the covered-way, or to 
 the small breadth of the demilune ditch, or to the steepm 
 the glacis, by which the batteries placed along its creel woald 
 be very much exposed to a reverse fire from the collateral 
 
 works, it shtould become necessary to place the breach ;m<l 
 counter-batteries on the terreplein of the covered-way, they 
 cannot be completed and armed before the seventeenth ot 
 eighteenth night. Although the batteries in this position 
 would l>e well covered from reverse five by the creel of the 
 glacis, and tiv.ni a think lire by the traverses of the eovered- 
 way, still, they would require much more labor to establish 
 them, and would be more exposed to the annovanee of gre- 
 nades thrown from the demilune. 
 
 After the descent into the demilune ditch is commenced, it 
 is steadily carried forward until it arrives at the point opposite 
 the breach, where the opening into the ditch Lb to be made 
 through the counterscarp wall; This opening should be pierced 
 at night, and the precaution Aould be taken to run a small gal- 
 lery along the back of the wall, on each side of the opening, 
 so as to plaeq a few men to lire through loop-holes made in the 
 wall, for the purpose of defending the opening, and the sap 
 
 |MlBhed RCrOSS the ditch to the breach. 
 
 ...K1..11 1 1 1 Mil, Nineteenth and Tu i \ m m Nighti 
 approaches from the fourth parallel and the crowning of the 
 sovered-way are pnshed forward and completed on these nia 
 
 It will seldom be practical. abliifa a trench cavalier 
 
 against the bastion salient place of arms, owing to thi 
 
 tire from the collateral demilune-. In luch a ease, it' the be* 
 
 d still occupy this work in foi 
 progress of I pi must be made to dislodj 
 
 by an open attack of a small party of picked tr< 
 
 stone-mortar batti ay be placed iu the position that would 
 
 be occupied by the trench i . by means of which 
 
 ged may be driven from this pail 
 So 'lie bastion cover* d-way i.- crowi 
 
'■'<'■'>>', ATTACK AND I'll I. Mi: OF lTUMAMNl WOStfB. 
 
 arc commenced into tile-maid ditch, from the trench at the 
 salient <>t' the covered-way. 
 
 In very acute bastions, the breach and counter-batteries 
 along the bastion covered-way might be completed on the 
 twenty-first night. But, generally, before this can be done 
 the demilune must be carried, as its tire would take these bat- 
 teries BO in reverse as to render their construction impracti- 
 cal ik-. 
 
 < J-4...T\vi:n i v-i-iitii XiNirr. The descent into the demilune 
 
 ditch and passage of the ditch may he effected by this nighl at 
 farthest. 
 Every precaution should he taken to prevent the besieged 
 
 from interrupting this passage. The passage itself should he 
 4 or 5 yards wide at bottom, to afford a convenient place of 
 arms for the troops, and it should be arranged with a banquette 
 to sweep the ditch by a close musketry fire. 
 
 Besides making loop-holes in the counterscarp wall to flank 
 
 the passage, it will also he Well to push forward one of two 
 zig-zags in the ditch itself, and place a small party of picked 
 men in them to repel the sorties of the besieged, 
 
 95^..The breach is gained possession of either by storm or by 
 gradual approaches. The former will he resorted to when the 
 besieged manifest a determination to keep possession of the 
 demilune, in force, to the last extreiuitv. A few Companies of 
 picked men will he chosen for this service. All the materials 
 will he collected at hand for crowning the breach, and, when 
 everything is in a state of readiness, a warm lire will he opened 
 on the breach and on all the works that in any way hear upon 
 it. At a preconcerted signal the fire will cease, and the 
 assaulljing column, rnshing through the breach, will drive the 
 besieged from the demilune, and then, sheltering themselves 
 as they best can from the tire of the other work,-, they will 
 maintain possession of the breach until the sappers, who follow 
 in their rear, can effeel a Lodgment on its top. 
 
 '.m;...Tu make the lodgment hv gradual approaches, the sap- 
 pers will push forward a sap from the foot of the- breach, over 
 
AT'fcW'K AM. T>1 I I \< I OF IMKMWIM WdHKI. 337 
 
 the ruin?, giving if nicb a direction as to gain a shelter under 
 the end of. the wall that remains on tin- side of the breach 
 which is exposed to the fire of the besieged. A?few picked men 
 •will cautiously mounl to the summit of the breach, occupying 
 such sheltered points as may be found at hand, for the pur- 
 of covering the sappers whilst at work. These men will 
 be sustained by a detachment posted along the pa the 
 
 ditch. 
 
 !<7...T\\ i n i Y-i\ i ii Night. The lodgment on the breach of 
 the demilune being effected on tins night, the breach :m<l 
 counter-batteries along the bastion covered-way, and against 
 the redoubt of tin- reentering place of arms, can be eompli 
 and armed. 
 
 A breach battery of 1 guns will be placed along cadi c 
 of the bastion covered-way, as far from the salient as room can 
 be had, for the purpose of opening as wide a breach as practi- 
 cable at the bastion salient. A. counter-battery, like.' 
 guns, will be placed along the same crest, and in the best p 
 tion t<» fire in the prolongation of the main ditch and bUi 
 the fire of the enceinte flanks opposite to them. A ln-cach 
 battery of 3 guns will also be placed each of the re- 
 
 doubts of the reentering place of arm.--, to oj.cn them on their 
 lace- thai lie adjacent to the dcmilunt 
 
 These bal ■! in Hank and rear in the same 
 
 manner as against the demilune. 
 
 I from attempting 
 besiegers from the demilune, it is well to ict a trei 
 
 acrof • from which the ditch of the demilnm 
 
 doubt can be swept by a fire of musketry, I 
 be made on tic i th night. 
 
 ►on a- the <i> iiiilwne breach : 
 commenced frotu the lodgment on it t ibt 
 
 until the thitf d night 
 
 In tin- 
 
 43 
 
338 .attack am> DEFENCE Of i'i:i;mam:m wokks. 
 
 and a doable Bap be formed in the parapet of the demilune it- 
 . to overlook the ditches and to approach the cut in the 
 demilune face 
 
 A descent can also be made on or before the thirty-second 
 night into the reentering place of arms, and a Lodgineift he 
 effected on itfe terreplein. 
 
 99.. .On the thirty-second nighty miners arc Bet to work at 
 the scarp wall of the demilune redoubt, and at the scarp and 
 counterscarp walls of the cut. The mines may be complete. 1 
 and fired, and the Lodgment he effected on the breaches by 
 the thirty-fourth night ; at which time the breach in the redoubt 
 of the reentering place of arms is also carried. 
 
 l(i(). .."When a breach can he opened in the bastion face 
 through the opening of the demilune ditch, the zig-zags in this 
 ditch mav he pushed forward nearly to the extremity of the 
 ditch, and the passage of the main ditch opposite the breach in 
 the salient he effected by the thirty-third night, so that the 
 breaches ill the body of the place, and those in the redoubts 
 and the cut can all he Carried on the thirty-fourth. But when 
 a breach cannot he made in the face of the bastion through 
 the demilune ditch, and it is deemed advisahlc to make one ;it 
 this point, it will he tfecesfiary to carry the outworks first, and 
 afterward to push forward the sap to crown the glacis of the 
 sinu'le caponniere in the demilune ditch, where u 1. reach bat- 
 tery of two guns may he established ; at the same time, a 
 lodgment is made behind the bastion covered face, and a 
 breach battery of 4 guns is established there. These Labors 
 Will require, for their completion, until the thirty-seventh 
 Bignt; In the meantime, lodgments are effected on the upper 
 
 and lower terrepleins of the demilune redoubt, and in its para- 
 pet, to overlook the main ditch, ihe double caponnicivs and 
 the tenailles. 
 
 The passages across the main ditch are also completed, the 
 descenl to the one nearest the shoulder angle being com- 
 menced from within the postern of the redoubt of the reen- 
 tering place of arms. 
 
attack \m> mil x.i oi rri:M\\!\i \\.:, 339 
 
 101...Tiiii:tv-i:i>.h nr Niter. The lodgment on the breaches 
 in the bastion will be effected on this night, and a descenl be 
 commenced from the top of the breach to the ditch of the cav- 
 alier. 
 
 1 "l'... Thirty-ninth lssd Fortieth Nights,. A lodgment will 
 be effected on the bastion terreplein, and a breach battery of 
 i {guns be established againsl each face of the cavalier. 
 
 The breach in the cavalier and the descent into the ditch 
 will be completed so that the final assault may be made on 
 the forty-first night. 
 
 DEFEM i:. 
 
 The object of this, like the preceding section, is to give a 
 succinct detail of the operations of the garrison during the 
 successive .-■ the attack, supposing the works which 
 
 they occupy provided with everything requisite for cond 
 iiig tin- defence vigorously. 
 
 LQ3. ..During the investment, the garrison will resort to ev< ry 
 mean.- for cutting off parties of the investing cdrpe which ap- 
 proach the work incautiously, and will particularly endei 
 t«> prevent all attempts at reconnottering. About one-thii 
 the garrison will l»e kept on this duty, tal 
 work "luring the investment and as long after as they 
 maintain their position without too gi 
 
 1 « ' 1 ... As i ' riod have no other danger to 
 
 apprehend than a si id nothii but 
 
 tillerywill l»e so posted ai I 
 most service in I 
 should be placed in 6m b ^ach flank, and mm 
 
 ynore on th( 
 
 lune-. with gi any at' 
 
 two or three he* , with lot 
 
 in barb< W of tin 
 
 lime-, to keep reconi 
 
 !".'■... W li.il' \ i : 
 
340 ATTACK AMI l'l I 1 N< 1 >>! IMI.'MAMNl WoKKS. 
 
 siegers to deceive the besieged, relative to the point of attack 
 and the time of opening the trenches, the latter, by keeping a 
 strict watch on all the movements of the former, are usually 
 
 enabled to ascertain both with tolerable certainty, and to pre- 
 pare themselves accordingly. So soon as these points are 
 known, the garrison, >till keeping mi the alert to frustrate all 
 attempts at Bnrprise, and without changing in any respect the 
 artillery already in position, will place all the disposable pieces 
 in reserve, in the best positions, on the fronts of attack ami 
 the collateral works, to do the most damage to the laborers 
 and the guard of the trenches before thev are placed under 
 cover in the first parallel. Fire-halls will he thrown outevery 
 night to light op the ground and ascertain the position of the 
 laborers and troops; ami, so soon as they are discovered, a 
 heavy tire of grape, etc., will he opened on them from all the 
 guns that can be brbtight to bear on their position. At the 
 same time, a few howitzers' Will keep up a ricochet lire in the 
 direction of the capitals to annoy the workmen at the ap- 
 proaches. 
 
 After an interval of two or three hours, the parapet of the 
 parallel will he proof against grape-fchot, mid then a lire of halls 
 and hollow projectiles will he commenced, and directed both 
 alonir the capitals and to take the guards and parallels 
 obliquely. 
 
 106... Unless the garrison is very strong, or the besiegers show 
 a want of proper precaution in covering their laborers by a 
 strong guard, sorties cannot he ma<h' at this period of the at- 
 tack with much prospect of success, owing to the distance of 
 the parallel from the defences. The most that ought to he at- 
 tempted will be to make soiHe charges of cavatoy, to cause the 
 laborers to stand to their arms, and thus retard, for a shorti 
 time, their operations. 
 
 K>7...AVhcn, from the indications without, there is no longer 
 any doubt respecting the real point of attack selected, all the 
 disposable artillery will be brought forward and placed in bar- 
 bette! in the best positions on this point and the collateral 
 
AIT A ik \\i> DEFJEJfOE 09 imkmwivi WtU&S. -".11 
 
 works, for sweeping the ground over wliich the (ranches must 
 be pushed. Tn the rneaiftime, embrasures, platforms and trav- 
 ersed arc prepared, oil the most suitable positions to place the 
 artillery under shelter so soon as Che enfilading batteries are 
 comph ted. 
 
 108.. .The following armamenl maybe taken as a mean for 
 this period of the defence : Eleven pieces in the bastion <>i at- 
 tack, one of which is an 8-inch howitzer, firing in the direction 
 of the capital, the others may be I s or 34-pounders, five being 
 placed on each face. 
 
 Seven or nine pieces of like calibre, and similarly di 
 may be placed In the cavalier of the bastion. 
 • Eleven pieces will be placed in each demilune of the attack. 
 one being an 8-inch howitzer to fire along the • , the 
 
 others 12 or 18-pounders, six of which arc placed on the 
 that bears on the ground opposite the bastion of attack ; the 
 other three on the other ' 
 
 Five pieces of heavy calibre on tli WW) collat- 
 
 eral bastions which bear most directly on the trend 
 their flanks which bear on the bastion of attack should i 
 receive four pieces near the angle of the cm-tain. 
 
 In the collateral demilunes, six pieces air placed on th< 
 alone that hear on the trend 
 
 the precedii n 8-inch howitzers should be 
 
 placed in th< >int of attack and of the 
 
 two collateral froi I — two being in each place of aru 
 in ricochet along the c:n- l \l>ont twenty 
 
 be distributed along the cm-tain-, and in tl 
 doubts. 
 
 The pieces on the fac< - which are enfila 
 : by gabionade tf 
 two 
 down, and the parapet l 
 
 loo. ...\n nninterrnpb 
 of the I 
 
342 ATTACK AND DEFENCE OF I'KKM ANKNT WOKKs. 
 
 commence throwing up the enfilading batteries. The fire 
 should be concentrated on a few of the principal batteries 
 rather than scattered over all, because, by delaying the prog- 
 ress of these, the odiers, if the besieged act prudently, will not 
 opeil their lire until all are ready. 
 
 llo.. .If the approaches are upl well defiled, or are directed 
 too near the salients, works, termed counter-approaches, may 
 he made from the covered-way to enfilade them. These works 
 are usually small redan Latteries, placed near the foot of the 
 glacis to receive the artillery in reserve not required for the 
 immediate defence of the work. They are connected with the 
 covered-way by an ordinaiy trench. These Latteries are kept 
 armed only during the day, and are protected by small detach-, 
 ments of about 50 men, to secure them from surprise. 
 
 111. ..During this period, the engineer officers and workmen 
 are employed in organizing the point of attack for a vigorous 
 defence. The covered-ways are palisaded with care. Tarn- 
 hours, or blockdioues, are estal dished in the salient place of 
 arms, and also in the reentering places of arms, if there are no 
 permanent redoubts. Similar arrangements are made in the 
 demilunes which have no redoubts; and interior retrench- 
 ments, cither of a temporary or permanent character, are made 
 in the bastion of attack. Easy communications are established 
 between all the works. 
 
 112. ..With regard to the portion of the garrison on daily 
 duty, the greatest number will be posted in the defences more 
 immediately threatened by the besiegers. About 40 men may 
 be posted in each salient place of arms of the point of attack, 
 and 20 in the collateral salients ; about 80 in each reentering 
 place of arms of the same point, and 40 in each of the collat- 
 eral ones. Besides these, there should he a detachment of 
 about 10 men in each demilune of the point of attack. The 
 number and disposition of the daily guard will of course vary 
 with circumstances. The main point to be attended to is v that 
 no part of the work, of any importance, shall be left without 
 a sufficient force to hold the besiegers in check, in case of sur- 
 
ATTACK AM" HI I IN' I OF ITI.'MWlNi WOl 
 
 prise, until support can be obtained from the main body, which 
 last should lie bo distributed as to be able t«» earn succor 
 promptly to any part threatened or attacked. « 
 
 118.. .So long as the besiegers are beyond musket range, tin' 
 guards in the covered-way have only to keep on the alert, ami 
 to send forward in the daytime a few picked men, who t 
 advantage of any shelter to approach the tren< I fire on 
 
 the workmen or guards who are exposed, and at night to keep 
 out patrols to scour the ground around the work : to annoy 
 the workmen when an opportunity offers, and to prevent the 
 approach of reconnoitering parties. So soon as the trenches 
 are pushed forward within musket range, an uninterniitted 
 warm fire ojF-nausketry is kept up on the workmen and guards 
 that are exposed, some 8 or ><> good marksmen being placed 
 in each salient tor this service. 
 
 H4...Sortiea may he made with more chances of sui 
 when the 1 nnaencc the second parallel, as the 
 
 iruai'ds of the trenches in the first parallel ai Dear at 
 
 hand to protect the workmen as during the construction of the 
 trenches up to this point. 
 
 The detachment tor the sortie, consisting of 3 or tOO infan- 
 try, will sally from the coverecr-ways to attack- the second par- 
 allel on one or both flanks, ami. if circumstam 
 front. Winn the workmen are put to flight, instead of pursu- 
 ing them into the first parallel, the ^etachment will form in 
 battle order to cover a party 1 hundred.- of work' 
 
 who follow in rear of the detach m< nt whilst they are till- 
 ing up the tn in roying the imp 
 fire to the gabions. The working party will b< 
 each flank by a detachment of infantry and all tin 
 ca\ airy of the place. Winn the 
 pear in force to repu rtie the I 
 without compromising tl d will i 
 the - in the pursuit within <h.. r t I 
 
 of which will }>< 
 iro,. from it. 
 
ATTACK ANH IT.I'l N< B OF IT.IIMANT.NT WuHKS. 
 
 may be repeated Beveral nights in succession; the best mo- 
 ment i> just before dawn, wheti the guards of the trenches are 
 fatigued and sleepy with watching. Although the chances of 
 success are greater at this stage than at the opening of tin- 
 trenches, still, it' the besiegers take proper precautions, the sor- 
 tie will, in all probability, prove more prejudicial than advan- 
 ous t.. the besieged, 
 
 115... Before the besiegers open the fire of the enfilading 
 batteries, the tire of the defences will be concentrated, as lias 
 been said, on the principal of these, and will he kept up 
 against them until a marked effect is observed in the tire of 
 the enfilading batteries. Only one gun will then he left be- 
 tween each traverse on the faces of the defences, the others 
 are withdrawn and kept in reserve. The guns and howitzers 
 kept in battery will fire steadily upon the heads of Che ap- 
 proaches as they are gradually advanced. 
 
 116... After the third parallel is constructed, the howitzers 
 may he replaced, with advantage, by stone and Cochorri mor- 
 tars, firing from the covered-ways and the redoubts of the re- 
 entering places of arms. Guns will be placed in embrasures, 
 to fire in the direction of the ditches of the demilunes of at- 
 tack against the crowning of their covered-ways. 
 
 117... At this stage, the musketry lire of the besiegers be- 
 comes very destructive to the artillerists whilst serving the 
 gnns. Strong oak musket-proof blinds should be arranged, to 
 mask the mouths of the embrasures when the guns are not in 
 battery. Blinds, or covers of timber and earth, under which 
 guns can lie secured from projectiles that Would reach them at 
 top or in flank, will now be serviceable. A few guns covered 
 in this way, and placed in the salients of the collateral works, 
 to obtain a reverse view on the trenches constructed on the 
 glacis, will prove a serious annoyance to the sappers, and will 
 greatly retard their progress. 
 
 118. ..The troops in the covered-ways will keep up a warm 
 lire of musketry against the heads of the sap, and on every ex- 
 posed point. The men firing occupying points where they 
 
ATTACK AM) I'M PI. KM \ \ I.NT WOE 845 
 
 will be best sheltered and can best see the leading sappers. 
 A few marksmen, will also occupy the parapets of the demi- 
 lunes and the redoubts, to keep up a fire from them, bnt only 
 during tlic daw as at night this fire might Injure the men in 
 the coveredjways. 
 
 The greater part of the guards of the covered-way should 
 now be withdrawn at night, and be posted in the deniilu 
 and redoubts, so as to expose but few troops if an attack by 
 storm is made. 
 
 119... Although sorties in Large bodies will seldom provi 
 cesst'ul after the second parallel is finished, those made by small 
 detachments of 1", 20 or .".<» men against the head of a sap, of 
 other work, when tic irs are advancing beyond the third 
 
 parallel, will seldom fail if conducted with proper precautions. 
 
 This method of annoyance will be particularly serviceable 
 during all the subsequent Btages of the defence, as the bet 
 ers camot now have at hand a very Large force. 
 
 120.. .The defence of the covered-ways will be regulated by 
 the method pursued in the attack. When the Latter is made 
 by gradual approaches, the troops, with the exception of a feu- 
 men who can find a shelter behind the short i . will be 
 withdrawn from the salient places of arms, 
 ace annoyed l>y the fire of the stone-mortars \ when this fire 
 which takes place when the sap id pushed forward 
 from the third parallel — the tro tin enter the salient 
 places of arms, and renew their fire on the heads of th< 
 directing it particularly against the - working 
 trench cavaliers. When the trench oavalii i 
 and armed, the troo om the sali< d< p 
 arms, and occupy the tra 
 maintain their fire, and throw hand grens 
 it comes within their I 
 also placed behind th< 
 
 121. ..If the to be mall ira- 
 
 fcions to attack bv storm, no a 
 to line the para; 
 44 
 
 ** 
 
346 ATTACK AND DEFENCE OF PERMANENT WoKKS. 
 
 more salient parts, and they should maintain their position no 
 longer than is necessary to give th'e storming patty one volley 
 as they debouch from the third parallel; retreating immedi- 
 ately after to the main ditch, or to other designated points. 
 A reserve of about 1(J0 men is posted in each reentering place 
 of arms, to cover the retreat of those from the salients. All 
 the other outworks are lined With troops, and such pieces as 
 can still be brought to bear on the glacis, loaded with case 
 shot, open, at the same time with the infantry, a deadly lire 
 on the storming patty; which is kept up until the assailants are 
 either driven from the covered-ways or take shelter in the 
 trenches constructed by the sappers along the crest of the 
 glacis. A vigorous sortie, botli on the front, the flanks, and 
 the rear of the storming [tarty, made from the collateral cov- 
 ered-ways, will, in such cases, be a judicious operation. 
 
 122. ..As the moment for crowning the covered-way ap- 
 proaches, the efforts of the besieged will be redoubled to re- 
 tard the works of attack. Independently of the measures al- 
 ready laid down, the besieged will arm with artillery the flanks 
 which bear on the point of attack, and will construct oblique 
 embrasures in the curtains, to sweep the positions along the 
 bastion covered-ways, where the besiegers are making the 
 breach and counter-batteries. The guards of the covered-way 
 will retire toward the reentering as the crowning of the cov- 
 ered-way advances, disputing the ground, foot by foot, and 
 holding possession of each point until the besiegers*are nearly 
 in a situation to envelop it with their works. The stone and 
 Coehorn mortars will be removed to the reentering places of 
 arms, or into some of the communications in the rear from 
 which a fire can be kept up on the trenches. In line, every 
 possible means will be resorted to by which the sappers con- 
 structing the breach batteries and the descents can be cut off* 
 and their labors be retarded. 
 
 123. ..When the besiegers have established themselves so 
 strongly on the glacis and the covered-way that sorties in small 
 parties cannot be made without too great risk, a warm fire of 
 
ATTACK AM) DEFENCE OF PERMANENT WORKS. .".IT 
 
 musketry will still be kept up od the trenches from all the 
 outworks, and the besieged will wait until the descent of the 
 ditch debouches at the counterscarp before renewing tin- same 
 game of sorties in small parties. A vigilant look-out will be 
 kept, to ascertain this moment, and so soon as tin sappers show 
 themselves, every effort will Ik 1 made to cut them off and 
 destroy their work, by opening a fire, both of artillery and 
 musketry, on the dchouehe, by sorties in small bodies, and b\ 
 throwing loaded shell.-, grenades, etc., into the ditch. 
 
 124. ..In wet ditches, filled with stagnant water, the besieg< d 
 will resort frequently to night attacks in boats on the dike or 
 passage ; and, in the case where water can he suddenly lei into 
 or be drawn from the ditch, chases of water will he aged to 
 sweep away the besieger's works. 
 
 KJ5...Irj defending the breach of the demilune, the besi 
 will resort, not only to the lire of it.- redoubt, but will erect 
 barricades on the right and left of the breach, across the demi- 
 lune terreplein, from which a warm fire of musketry will be 
 ponged in on the besiegers whilst they attempt to gain ]>"- 
 sion of the breach either by gradual approaches or by storm. 
 Small mines, or bomb fougasses, should be prepared at the 
 summit of the bread]. t<> be exploded .-■> soon as the I 
 gain possession of it. Die top of the breach will be strowti 
 with every possible obstacle that can retard the progress of 
 the storming party, and grenades, thundering-bari . will 
 
 be rolled over ou the troops whilst mounting the breach. 
 
 L26...The measures for the defem t' the main ditch and of 
 
 the breach in the bastion face, differ 1 in nothing from t 1 
 
 rted t<> for tin- demilune. Xhe b will mal 
 
 efforl to keep possession of the ditch to the tn>t moment, b • 
 enpying the double caponnii 
 of which works .'ire will h. kept tip 
 
 whilst effecting the p 
 troops will be frequently made nnder Ui< 
 
 by the lire of the t< nuh 
 
 require to he guarded with | 
 
348* ATTACK AND DEFENCE OF l'KKMAM NT WORKS. 
 
 besiegers carrying them by surprise, and thus effecting an en- 
 trance into the interior of the work. 4 
 
 1l'7...Aii assault of the breach in the bastion cannot be op- 
 posed by the bayonet without compromising the lines of the 
 garrison, unless there exists a good interior retrenchment to 
 cover the retreat from the breach ; even in this case, to oppose 
 the storming party with the bayonet will be an operation of 
 great delicacy, for the besieged, if driven back.'niav not be 
 able to effect their retreat without being so mixed up with the. 
 assailants as to render it impossible to prevent the latter enter- 
 ing with them into the retrenchments. 
 
 128. ..Finally, when the breach is effected in the interior re- 
 trenchment, the besieged may offer to capitulate, unless they 
 are still able to protract the resistance a day or two by organ- 
 izing temporary defences, and by placing the houses u> the 
 rear of the retrenchments in a defensive state, in which cases 
 this breach should be disputed with the same obstinacy as 
 those of the other works. 
 
 RELATIVE STRENGTH OF THE GARRISON AND 
 BESIEGING FORCE. 
 
 As a permanent work should force "an enemy to resort to an 
 attack by regular approaches, its garrison should be at least 
 of sufficient strength to prevent its being carried by a coup de 
 main or open assault. The largest garrison will depend upon 
 the means provided within the work for lodging troops, and 
 securing properly the munitions of war requisite for the num- 
 ber that can be accommodated during the presumed duration 
 of the defence. Between these two limits the best military 
 authorities estimate as a medium garrison, capable of making 
 a good defence, 000 men per front, or bastion ; this force being 
 composed of the different arms of the service in the proper pro- 
 portions for the duties required of them. AVhen the defences 
 comprise, besides the enceinte, some of the principal outworks, 
 and it is intended to occupy them strongly, with a view to an 
 
ATTACK AMMUMMT 01 I'KI.'MAMM WOBK8. 349 
 
 ttctive, vigorous defence, an allowance from 900 to L,< men 
 
 should lie made per bastion. 
 
 189..."With rerfpect to the quantity of artillery necessary for 
 the armament of a permanent work, there is considerable dis- 
 crepancy 6f opinion among military writers. A resolute gar- 
 rison might preserve a work of tolerable strength from a coup 
 dc main without the aid of cannon; and an idea of the 
 largest amount of artillery might be arrived at. by BUpp< 
 each front to lie armed with as many pieces a- it cdfo carry, 
 with the addition of a suitable number of pieces in reserye to 
 provide for casualties. But these are inadm 
 and a medium estimate is to allow ?, heavy guns and 
 heavy mortar per front or hast ion, with 60 heavy guns, 20 
 heavy •mortars and 10 stone, or light mortars, for the arma- 
 ment of the point of attack. 
 
 In estimating the amount of ammunition, an allowance of 
 1,000 rounds is made for each j£un, 800 rounds for each mor- 
 tar, loo musket cartridges per day for each soldier <>n guard ; 
 and .".on pounds of powder for each mine. 
 
 130.. .The strength of the besieging force is baaed upon that 
 of tlie garrison. Hie usr.nl estimate is to allow, for the daily 
 duty of the trenches, at least as many troops a- the gavrif 
 including in this number the men employed in making the 
 trenches. As the service of the b ery onerous, the 
 
 tour of duty in the trenches should not he me re fn quent than 
 once in five or six days. Admitting this i 
 ing force, comprising all arms, should he 
 Btrong a- i!i.' garrison. 
 
 1 - *» 1 ... 1 1 1 estimating tin- quant many 
 
 guns and mdrtara are allowed foi 
 mortar batteries a- tli.' presumed armament i 
 
 tack ; with an addition . »1 
 batt. I 
 The medium allowance of ammunition for tl 
 
 1,000 rounds tor • 
 
 L82...I1 i.- hardly i • 
 
350 ATTACK AND DEFENCE OF PERMANENT WORKS. 
 
 mates are of a very general character, and are introduced here 
 merely to give some idea of the relative proportions in ques- 
 tion. Before undertaking the siege of a work, no pains should 
 be spared to gain all the information possible respecting the 
 state of its defences, and the probable difficulties to be encoun- 
 tered in i,ts attack, and the estimates based on these data 
 should be made on the supposition of the work being provided 
 with all the means of a vigorous defence. 
 
 Remarks. In the preceding description of the methods of 
 attack employed against permanent fortifications, the calcula- 
 tions for the extent and strength of the trenches and batteries 
 have been based upon the range and effects of the artillery 
 and small arms which were in general use in siege operations 
 up to the recent important changes and improvements which 
 have been made in the efficacy of arms and projectiles of every 
 character. What corresponding changes in the methods of 
 attack will be called for, arising from these improvements, 
 special experiments and the experience derived from future 
 sieges can alone determine. 
 
 From the very ample official records of the siege of Sebas- 
 topol. where the armament of the defensive works consisted, 
 in a great measure, of the heaviest calibre of ships' guns, it 
 would seem that no very marked deviations were made, either 
 by the French or English, from the methods of attack used in 
 previous sieges. The first parallels were commenced at about 
 700 to 1,000 yards from the positions of the defences, and the 
 trenches were, for the most part, executed by the flying sap; 
 the full sap being used by the French sappers alone, and only 
 when they had approached very near to the defensive 'works. 
 Owing to the peculiar difficulties presented by the character 
 of the ground, the defensive armor prescribed for the leading 
 sappers in executing the full sap was laid aside to Enable the 
 men to work more effectively. 
 
 In the construction of their batteries, the French appear to 
 have deviated only in exceptional cases, arising from the 
 nature of the site, from the dimensions and constructions 
 
ATTACK AND DEFENCE OF PERMANENT WORKS. 351 
 
 which had beeD previously adopted by themi The English 
 engineers, from their experience in this Biege, are in favor of 
 thicker parapets, and a greater exterrt of'frontfor each gun f<»r 
 batteries, particularly for the heavy calibres of ships' guns 
 with which Borne of their batteries were armed. These, with 
 a few minor changes in the details of platforms and emhra- 
 sures, are the only modifications in the Siege works of any im- 
 portance which the results of this memorable si ■ . a to 
 have Suggested. 
 
 In the defence of their trenches from the frequent Borti( - 
 the garrison, the French, after meeting with BeriOus losses in 
 the earlier stages of the Biege, from the impetuosity of their 1 
 troops in Bally ing upon the enemy beyond their tren< 
 finally adopted the sale rule laid down by Yauban of quietly 
 withdrawing the guards from the portion t of trenches upon 
 which the sortie was directed, with the view of assailing the 
 enemy so soon as they had got within them and whilst in a 
 confused and broken condition. This plan met with full - 
 and was found most effectual in restraining thi 
 
 In their defensive works, which were almost entirely 
 temporary character, the Rue Idopted for their parapets 
 
 the ordinary dimensions for resisting the 1 
 
 'Although subjected to an i no- .--an t and terrible lire of the 
 
 heaviest ships' guns, with which the 
 
 armed, these parapets, with Buck daily care as could 
 
 in repairing their damagi b, Beem to ha> e afforded am] 
 
 to the garrison from the direct fire. I 01 
 
 fire, resoii was had to blindages, formed, in 
 
 nook, with the heavy timbers, furnished by the dock-ya 
 
 which, being I with a thii 
 
 earth. Beem to have an- 
 
 shelters from the shocks of the h< 
 gunners from the em 
 sians convert d the h< avy rop< --it 1 ,' 
 a kind of matting, w hich was, in 
 
 mouth of the embra 
 
352 ATTACK AM) DEFENCE OF l'l'.UMANKXT WOBKfi. 
 
 made of a circular form, with a hole in the centre large enough 
 to admit the chase of the gun, to which it was fastened as a 
 
 screen for the men at the trail. 
 
 Owing to their ani]>le garrison, the Russians were enabled 
 to take up and fortify several strong, isolated positions, in ad- 
 vance of their continuous line of works, after the siege opera- 
 tions were well under way. They also nsed with great advan- 
 tage Btnall troups-de-loup,oY pits for sharp-shooters, in advance 
 of their line, from which both the workmen at the trenches 
 and the artillerists of the besiegers were greatly annoyed. 
 These were in some cases connected and formed into a con- 
 tinuous trench of counter-approach, from which they, were sub- 
 sequently driven only after considerable loss to the besiegers. 
 
> 
 
 J>-> >:s> ^»5s 
 
 
 
 
 
 
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