170 MILITARY SCIENCES. 



dug down three feet, and applied to the formation of the breastwork. Mean- 

 while other workmen establish between the barbettes, A and GH, a sap 

 with gabions, z, which, filled with earth, afterwards support the sleepers of 

 the platforms. The ramps, B, are also dug, and the mass of earth, U, three 

 feet deep, in front of the battery, is thrown up on the parapet In rear of 

 the battery, two magazines, D, are established. The line of direction of an 

 embrasure, when the parapet is completed, is determined, under the hostile 

 fire, as shown on jpl. 49, fig. 36. To the laths, ah, the rods, ac and hd, are 

 fastened, the laths laid upon the superior slope, in rear, exactly on the mid- 

 dle line of the embrasure, and by moving the foremost end of the rod, hd, 

 sighted into line, this line is prolonged backwards by sighting-in the stakes, 

 ef. The direction of the cheeks {pi. bO,fig. 3), ce and df, is obtained by 

 laying off upon the prolonged line of direction, ah, from seven to eight feet, 

 and digging out the cheeks in the prolongation of gc and gd. If the line of 

 direction of an already completed embrasure is to be changed, a new line 

 of direction is first determined, and then either the embrasure alone is 

 merely moved (fig. 4), or the parapet is cut into, or an oflfset made upon it 

 {figs. 5,6). A horizontal battery in the parallel, built out of the range of the 

 enemy's fire, is shown in fig. 44, which gives the ground plan, and ^^. 45, 

 which presents the section. W is the parallel, GH the fire line, A the battery 

 platforms, U the ditches, N the ditch of communication in rear of the battery, 

 BCE are entrances, D the magazines. Of a horizontal battery in rear of the 

 parallel (fig. 40 shows the ground plan,^^. 41 the section). W is the paral- 

 lel, GH the parapet, UU the ditches of communication, which are protected 

 by the parapets, M ; D are the magazines, V the ditches ; the piece, NO, of 

 the parapet of the parallel, is cut out and covered by the barbettes, PP. 

 Fig. 32 gives an example of a sunken battery in the parallel. It is for three 

 12-pounders and one mortar. GH is the parapet (with embrasures accord- 

 ing to fig. 33, if) ; B is a traverse, which separates the mortar from the 

 cannon ; N the ditches of communication, and D the magazines. Fig. 38 

 is the ground plan, fig. 39, the section of a sunken battery, oblique in front 

 of or behind the parallel. The signification of the letters is the same as in 

 the preceding figure. GI is a piece of the parapet, which is raised higher to 

 cover the battery. The arrangement of the elevated battery is shown by 

 the ground plans (figs. 34, 36), and the sections (figs. 35, 37). Here, a 

 piece of the parapet on the side towards the hostile fire must always be 

 carried up at the same time for a cover. In figs. 34 and 35, the pieces fire 

 en barbette ; in figs. 36 and 37, through embrasures. Fig. 31 is a rear 

 view of a battery of 24-pounders before the Algerine fortress of Constantine. 



2. Defence of Fortified Places. 



So soon as the front of attack is known, it is properly armed, and embra- 

 sures are everywhere cut, when the construction of service magazines, for 

 daily use, is at once proceeded to. Fig. 48 shows the arrangement of such 

 a magazine, on a dry bottom. The timber- work is composed of the sleepers, 

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