FORTIFICATION. 15] 



counterscarp, the inner the scarp. Between the breastwork and the scarp 

 an off-set is left (fig. 22 a d) called the berme. The slopes must be revetted 

 whenever possible, either with sods or with fascines, wicker-work, gabions 

 or boards {fig. 21, pp), or with trunks of trees (fig. 22,pp). To secure the 

 slope, /^ (j^^. 23), against being mounted, it can be palisaded, by setting 

 trunks of trees, w, 10 to 12 inches in diameter and 10 to 12 feet long, 4 to 5 

 feet in the earth, at g, and sharpening them at the top. Trunks of trees may 

 may be also set obliquely in the berme space, as ^y at r (fig. 23). These 

 are called fraises, and are secured above by a transvere sill, t. The inte- 

 rior slope of the breastwork (ab, fig. 21) is very steep (12 to 18 inches) in 

 order that the soldier may get near enough to the crest, af. The banquette 

 for the defenders, b c, is regulated in breadth according to the number of ranks 

 it is to contain, and varies from 3 to 7 feet (figs. 21, 22, 23, 24). Its slope, 

 dc, is regulated according to the elevation, and where the rampart is very 

 high is made in steps (fig. 22). If the work is to contain cannon and the 

 banquette is not wide enough to receive them, an especial banquette (bar- 

 bette) is constructed for that purpose, provided with ramps. Figs. 29 — 34 

 show such barbettes. Fig. 29 is a simple barbette, X, upon a face or 

 flank. Fig. 30, a ramp for mounting the terre-plein or broad banquette. 

 The axis of the ramp, wpv, is perpendicular to the line of fire. Fig. 31 is 

 a narrow barbette for three pieces, Y X Y, in the salient of a bastion, which 

 is cut off at w V ; tp and wvaa are the platforms for the guns. Fig. 32 is 

 a wide barbette, for three platforms, w v and tp, for the pieces, X and y, in 

 the bastion salient. Fig. 33 is a narrow barbette for one platform, w v, for 

 a single piece, X, in the salient. Fig. 34 is a wide barbette, for one piece, 

 X, for side defence, in the salient ; vw is the pan coupee of the salient, b z, 

 for infantry. If the barbettes are not high enough to permit the pieces 

 to fire over the crest of the breastwork, af (fig. 23, to fire en bar- 

 bette), then embrasures must be cut for them which are wider in front than 

 in rear, and are either direct or oblique on the line of fire. The inner 

 openings of embrasures are blinded, either by hurdles set before them or by 

 a shutter, A (pi. 47, fig. 35), where two posts, gg, with a cross tie, m, are 

 secured into the parapet on which the shutter. A, hangs by hinges and sta- 

 ples, X. The sides of embrasures, called their cheeks, are revetted, either 

 with fascines or gabions. The superior slope of the parapet, af (fig. 24), 

 is so drawn that its prolongation strikes the surface at the point i, unless 

 there is upon the counterscarp a second parapet, i kp g, for defence, when 

 the prolongation of the superior slope must strike the point j9. The space 

 between the counterscarp and the parapet, i kp g, is called the covered way. 



If circumstances require that a work be so placed that from neighboring 

 points it can be overlooked and fired into (commanded), then traverses 

 tkil (fig. 36) are constructed in the interior. The passages e e are covered 

 by small mounds of earth (tambours) z. Such tambours are placed also 

 before the entrances of works. Over the ditches light bridges, y, are carried. 



e. Internal Defences. In great works there are other interior defences 

 constructed, by means of which the garrison can maintain themselves for a 

 time, even after the main work has been carried. Such works are called 



627 



