FORTIFICATION. 



pets, should be regularly mown fur the 

 same purpose. 



The counterguard B is solid, as is 

 also the rampart A; its terre-pleine H 

 is considerably lower than that of A, 

 which commands it, both by the cannon 

 it mounts, and by its musquetry; the 

 parapet being 1 sloped so as to give a di- 

 rect fire into it, when the firelocks are 

 laid upon the slope at x. In this coiui- 

 terguard the interior of the parapet is not 

 reveted; therefore the banquette I, as- 

 cended from the terre-pleine, H, by a 

 slope of gazon. The parapet C, &c. 

 are nearly the same dimensions as F on 

 the rampart A, except that the i*ampart 

 B is much lower than A. The exterior 

 of B has a cordon, level with the terre- 

 pleine H, but its parapet is faced with 

 turf, which the cordon assists to sup- 

 port. If the counterguard B were not 

 defended by other out-works in its front, 

 it would have a glacis come close to it, 

 leaving only a very small passage be- 

 tween its exterior and the palisades; 

 here we suppose it to have a small dry 

 ditch D, reveted both in the scarp and 

 counterscarp, but without a berm, which 

 is very rarely, if ever, allowed to an out- 

 work. 



The third figure affords a more gene- 

 ral profile of the works, and gives some 

 idea of the usual defilement of the out- 

 works, B and C, from the body of the 

 place A. D is the foot of the glacis, 

 where it meets the terre-pleine, or level 

 of the country, which we always sup- 

 pose to be esplanaded, (that is, laid flat) 

 and not affording any cover to the ene- 

 my for at least 1'JOU yards from the out- 

 works. The glacis is usually made full 

 50 yards long, and of such an ascent as 

 to give, on an average, about eight feet 

 heigh at its crest. Supposing the angle 

 of the raveline to be 25 yards within 

 the crest of the glacis, the continuation 

 of the ascent would strike the cordon 

 of the rampart, C, at 12 feet from the 

 level of the terre-pleine ; this determines 

 the height at which a cannon, standing 

 on the terre-pleine of the raveline, C, 

 would graze the glacis, while the slope 

 of the embrazures would allow the guns 

 to play into the covert way. It is ob- 

 served, that, according to this construc- 

 tion, all the scarp, below the cordon, is 

 completely hid from the enemy, and can- 

 not be battered, so long as the crest of 

 the glacis remains at its proper height. 

 Hence partly arises the great difficul- 

 ty of breaching the saliant angles of out- 

 works. 



VOL. V, 



Now let us estimate the redoubt, B, 

 at 25 yards within the flanked angle of 

 the bastion C. It is to be remarked, 

 that this defence is made with the view 

 to render the raveline untenable to an 

 enemy; and that, for the preservation 

 of its parapet, the rampart of the re- 

 doubt, B, should be a mere trifle above 

 the level of that of the raveline, C. 

 The faces of the contiguous bastions of 

 the same front enfilade the faces of the 

 raveline ; but it is always requisite, that 

 the fire from the curtain should, on emer- 

 gency, (for the bastions may be silenced) 

 contribute to drive the assailants from 

 that part of the raveline which lays be- 

 yond the redoubt ; at all events to clear its 

 ramparts. Therefore we will state the 

 terre-pleine of B at only one foot above 

 that of C. This puts the redoubt com- 

 pletely out of the line of defilement, and, 

 in fact, generates another, by allowing the 

 curtain, A, to throw shot into C, with- 

 out touching any part ofB, as may be 

 seen by following the line from the cor- 

 don of A to the terre-pleine of C. 

 Hence B cannot be battered from the 

 glacis. 



But where it is necessary to produce 

 the greatest accumulation of strength 

 against any exterior point, it is often 

 found proper to raise every part of the 

 interior defences, so that they should all 

 overlook, like a flight of steps, as shewn 

 in fig. 4, where the citadel is supposed 

 to stand on a conical hill, high above 

 the town, (which is only defended by a 



flacis and covert way, surrounding a 

 itch and rampart) and has four rows 

 of cannon, at different heights, each com- 

 manding the exterior defences, and the 

 surrounding country, as far as the shot 

 can reach. This, though not a com- 

 mon figure, nor a common mode of for- 

 tifying such places, (for works are rare- 

 ly carried like hoops or bands around 

 hills) will fully illustrate the general ten- 

 dency of the foregoing details, and to the 

 ordinary reader, who cannot here expect 

 to find all the minute items and varieties 

 abounding in this very intricate science, 

 will give a tolerable insight into the prin- 

 ciples on which fortifications are usually 

 constructed. 



To return to fig. 3. It will be seen 

 that the elevation of A would, on the cal 

 culation there assumed, be such as to 

 carry the cordon of its terre-pleine so 

 high, that its revetement could be bat- 

 tered from the glacis, DO, without touch- 

 ing C or B. To remedy this, where such 

 an exposure would be injurous, (for it is 

 Dd 



