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FORTIFICATION. 



FORTIFICATION. 



174 



main ditch. But his principal improvement consisted in extending 

 the covered way and glacis along the whole of the enceinte, and in 

 placing the ravelin with its proper covered way and glacis on the 

 exterior; in consequence of which disposition it would become 

 impossible for the besiegers to breach the bastion by firing along the 

 ditch of the ravelin, while the latter would possess all the advantages 

 attending the greatest possible saliency. The ideas of Bousmard 

 respecting the disposition of the ravelin were adopted by General 

 Chasseloup de Labat, in the works which he executed, by order of 

 Napoleon I., to strengthen the fortifications of Alessandria ; and the 

 same engineer constructed a strong polygonal redoubt of earth in each 

 of the places of arms before the flanked angles of the bastions and 

 ravelins, in order to increase the quantity of crossing and reverse fires 

 in front of the works. 



The last modification of the bastion system which it will be 

 necessary to mention, is that proposed by Choumara, who, partly to 

 diminish the pressure of the parapets on the escarp revetment, and to 

 render the formation of a practicable breach more difficult, and partly 

 to procure a close fire of musketry into the covered-way, suggests that 

 a terreplein, like the old chemin des rondes, but with a slender breast- 

 work to protect the defenders, should be left on the exterior of the 

 parapets. The same engineer recommends that the flanks of the 

 bastions should be lengthened by continuing them within the line of 

 the curtain, and that they should have a greater relief than the latter, 

 in order that a fire of artillery might be directed over it against the 

 works of the enemy : he proposes also that a glacis of earth should be 

 raised in the main ditch, high enough to mask the foot of the escarp 

 revetment, and prevent it from being battered by a fire of artillery on 

 the crest of the covered way. 



As early as 1640, Dillichs, in a work published at Frankfurt, 

 proposed a method of fortifying places, which consists in surrounding 

 them by lines of rampart forming with each other a series of angles 

 alternately salient and re-entering, being in fact a Teuaille system ; and, 

 subsequently to the time of Vauban, a few other projects of a like 

 nature have been suggested. The most remarkable of these is that 

 which wag published in 1776 by the French General Montalembert, 

 who entitles his method ' Fortification Perpendiculaire.' Its outline 

 on the plan is a series of the sides of equilateral triangles formed on 

 those of a dodecagon inclosing the place ; the re-entering angles being 

 consequently right angles, and, as the general has developed some 

 useful ideas concerning the interior defence of a place, though no 

 existing fortification affords an example of the method, a short descrip- 

 tion of it may with propriety be given. 



Three parallel ramparts of earth, of the form above indicated, and 

 separated from one another by wet ditches, surround the place : the 

 berme at the foot of the first and third is protected by a simple wall, 

 and that at the foot of the middle rampart is covered by a loop-holed 

 gallery on its whole length. Beyond the outer ditch is the covered- 

 way, whose re-entering angles are fortified by strong redoubts. In the 

 re-entering angles of the two interior ramparts are formed casemated 

 batteries, the fires from which would sweep the surface of the ditches 

 in front, in the directions of their lengths ; and, within the enceinte of 

 the place, a circular redoubt, or tower, of brick-work, carrying several 

 tiers of guns, is intended to defend the interior rampart, if, at length, 

 it should be forced. The merit of this system is supposed to consist 

 chiefly in the powerful fire which the casemates would afford, as from 

 their situation, they would scarcely be injured by the enemy; in the 

 difficulty which the latter would experience in getting over the de- 

 tached walls ; and in the great force which the defenders, by means of 

 the spacious communications, might bring up to oppose the assailants. 

 During the existence of the first French empire, the celebrated Carnot 

 proposed to restore the balance between the attack and defence of 

 fortresses, which the inventions of Vauban had made to preponderate 

 greatly in favour of the former, by means of powerful sorties from the 

 place and an abundant discharge of stones and balls from mortars fired 

 at considerable angles of elevation ; thus annoying the besiegers in 

 their trenches, and either putting great numbers of their men hors de 

 combat, or compelling them to recur to the slow process of blinding 

 their approaches. Adopting, in his method of fortifying places, the 

 proportions of Cormontaingne for the plan of his bastions, but making 

 the whole length of his front of fortification equal to 480 yards, he 

 detached the bastions from the enceinte, which he made to consist of 

 a simple polygonal rampart of earth. In rear of the tenaille between 

 thu bastions he placed a fausse-braye, whose exterior side was to be 

 protected by a casemated tower at each extremity ; and, behind the 

 gorge of each bastion, he formed a row of casemate vaults, in which 

 the mortara were to be placed for throwing stones, Ac. into that work 

 when gained by the enemy. Adopting also the ideas of Montalembert 

 respecting detached walls, he proposed to surround the enceinte by 

 one, which was to be loop-holed in order that a fire of musketry might 

 be made from it, and to construct a similar wall before the faces and 

 flanks of the bastion*. The bastions were to be covered by narrow 

 counterguards ; a cavalier, or lofty redoubt, in front of the tenaille, 

 was to defend the collateral faces of both bastions and counterguards ; 

 large ravelins were to cover the central parts of the fronta of fortifica- 

 ud afford crossing fire* un the ground before the bastions; while 

 mortars placed on the face* of the work and on the barbettes at the 

 angles were to discharge their missiles over the parapets. A ditch 



surrounds the whole, and its exterior side is made with a gentle slope 

 from the bottom to the level of the natural ground in front, for the 

 purpose of facilitating the sorties ; the corresponding facility which 

 the enemy might have for descending into the ditch being disregarded 

 on account of the supposed impossibility of maintaining himself there 

 under the hail of stones and shot from the works. 



It was supposed that the detached wall, being covered as before 

 mentioned, would present an impassable obstacle to the assailants ; but 

 an experiment made at Woolwich in 1824, proved the possibility 

 of breaching it by a fire of shot and shells, directed over the parapet 

 of the counterguard, from artillery of great calibre, at the distance of 

 400 yards from the latter work. The efficiency of the vertical fire, as 

 it is called, of stones and shot from the works has also been contro- 

 verted^ and experiments have been made which seem to prove that 

 the momentum acquired by the missiles in their descent would not be 

 sufficient to do serious injury to a man on whom they might fall, if he 

 were protected by a proper head-piece. 



We now come to what is variously termed the polygonal, right-lined, 

 German or Prussian system. It has of late years been much adopted 

 by German engineers, but has never yet been tested by an actual siege. 

 Instead of the ramparts of the enceinte being broken up into bastions 

 and curtains, they follow the lines of the polygon and are flanked by 

 projecting masonry works called caponnieres, something like Vauban's 

 tower bastions, or Montalembert's casemated batteries, from which they 

 are taken. The lines of defence may be about 300 yards, so that 

 placing the caponniere in the centre of the side of the polygon this 

 may be taken at 600 yards. The caponniere, projecting about 35 yards 

 from the exterior, will contain 12 guns in 2 tiers of casemates on each 

 side, that is twice as many as an enemy can place in a breaching bat- 

 tery against it; and if built with an interior court for ventilation 

 would be about 30 yards in width. The caponniere is covered in front 

 by a simple counterguard, or by a strong ravelin, and its sides flanked 

 by gun casemates in the enceinte, the ravelin being flanked in the 

 same way, or by casemates at its gorge. The detached escarp has 

 commonly been employed in this system, of which perhaps the best 

 example is Fort Alexander at Coblentz. 



Besides these already mentioned, many ingenious systems have been 

 advanced at various times, among which may be mentioned one by 

 Lieut. Cook, late Professor of Fortification at Addiscombe College ; 

 Mr. Bordwine's system, and, still later, a further development of this 

 latter by Mr. Fergusson. Mr. Fergusson's system has of late received 

 so much notice from the able manner in which he has advocated it, 

 that it would appear to require some description in this place ; but in 

 the limits of this article, though some idea might be given, it would 

 be impossible to do it justice; the reader is therefore referred to 

 ' Fergusson's System of Fortification." It may be remarked, however, 

 that ingenious as it undoubtedly is, and remarkable as are some of the 

 ideas propounded, it has not attracted any large amount of support 

 from engineers either in England or on the Continent ; and though 

 the author appears to attribute this principally to professional jealousy, 

 &c., it must be acknowledged that it could hardly be carried out in its 

 entirety, nor would it be likely ^> fulfil his anticipations. It is neces- 

 sary to guard against the idea, in discussing the system, that the 

 Russians employed it, and with such great success, at Sebastopol. 

 This confused idea appears to have originated from the fact that Mr. 

 Fergusson proposes a huge mound of earth divided into numerous 

 parallel ramparts, and that the Russians used earth-works, though the 

 former proposes to sprinkle his ramparts pretty freely with casemates, 

 and the latter used unrevetted earthworks because they could make 

 no other, and followed the ordinary plans which have been followed 

 for centuries in field fortifications or entrenchments ; never raising tier 

 above tier of guns, except where occasionally one battery erected 

 behind and on considerably higher ground fired partially over one in 

 front. This may be easily seen by a very cursory inspection of the 

 plans. The immense duration of the siege of Sebastopol is easily 

 accounted for, when we remember that a large and powerful enemy, 

 never numerically much inferior and occasionally superior to that of 

 the allies, was defending in a naturally very strong position one of the 

 largest and best supplied arsenals in the world, from which they ob- 

 tained guns and ammunition in greater numbers, and of larger calibre, 

 than the allies had, almost to the last, to bring against them ; that 

 their rear and communications were open, so that casualties could be 

 replaced; that they had a powerful fleet in their well-fortified har- 

 bour, and a great number of the ships of which being sunk supplied 

 them with artillerymen ; that they had a large army of observation 

 in the field constantly harassing the allies, and threatening, by such 

 sorties as at Inkermann, to raise the siege ; and, lastly, that even on 

 the approach of the allies on the south side, they had sufficient per- 

 manent works, as the crenelled wall on the west, the central bastion, 

 the Malakoff tower, Ac., with their ships, to make a coup de main 

 hazardous, if not impracticable, and thereby by obliging the allies to 

 make batteries and bring up guns to destroy these, giving themselves 

 time, which they certainly availed themselves of, to erect counter 

 batteries and perfect their defences. 



It is scarcely probable that any existing fortresses will be demolished 

 for the sake of the advantages which would result from a re-con- 

 struction according to any of the methods which have been proposed 

 since the time of Vauban ; but, on any future occasion which may 



