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were only used in conjunction with the latter. The most remarkable instance of this admixture of systems was the memorable siege of Constantinople, by the Turks, in 1453, full details of which will be found in the present volume. Fourteen batteries of guns, among which were three pieces capable of throwing stones weighing from 600 lb. to 1200 lb., were pointed against the double walls and towers of ancient Byzantium; but, employed in addition, were engines for throwing darts, and rams for battering walls; and the broad ditch being at length filled up, a moveable turret was advanced on rollers up to the walls, where, however, it was destroyed by the fires of the besieged. The guns of the Greeks are said to have been of small calibre, the ramparts not being broad nor solid enough to permit the use of heavy artillery upon them. Annexed are four representations of ancient guns as given by Valturinus, Uffano, and others. One, the tube of which is partly horizontal and partly vertical, is called the "elbow piece," which Grose ("Military Antiquities,") from whom we copy our engravings, says, "probably only existed in imagination."

SPECIMENS OF EARLY ARTILLERY.

In course of time, as the calibre of artillery became greatly increased, and iron balls were substituted for blocks of stone, it became apparent that the system of defence must be altered to meet these more formidable weapons of assault. As a principle, it was soon discovered that, beyond a certain point, fortifications derived no additional strength or security from the height of their walls, which battering cannon could effectually breach; but rather in extending the defences in front of the walls by means of ditches and outworks, so as to keep the besiegers at a greater distance; the ramparts being reduced to a lower level, so as to be as far as possible concealed and protected by the extended outworks.

Nevertheless, the changes so suggested were not suddenly effected; the first attempts to meet the new difficulty, as evidenced in the works of the fifteenth and sixteenth centuries, were rather to add to and remodel portions of existing fortifications, in which the lofty walls and angle-towers, and the ancient drawbridge, with its barbacan appendage, were still retained. At the siege of Metz, for instance, A.D. 1552, the Duc de Guise, who commanded, raised mounds of earth outside the single turreted wall of the town, with parapets formed of large gabions, upon which to plant cannon; and within the walls, which were breached by the enemy in several places, he erected retrenchments of earth, strong enough to resist cannon-shot.

THE BASTION SYSTEM.

At length a new and important change took place in the very principles of fortification, by the introduction of the bastion and its ravelin. And here it must be explained that the portion of straight wall between two towers, or fortified angles, is generically styled a curtain; and it soon became apparent that the ancient towers were no longer able to protect these portions from the artillery of the besiegers. The plan then adopted, was to substitute for the towers large earthworks, called bastions, having two faces and two flanks each; and to construct between each pair of bastions, and in front of the curtain, another projecting earthwork, called a ravelin, in level somewhat lower than the bastions, the guns of which should 66 cover the approach to the bastions themselves, whilst they directly defended the approach to the curtain.

The

We owe the first attempts at the bastion system to Italian engineers, and their example was afterwards followed in the Netherlands, France, and in the Continent generally. Among the earliest who treated on the subject, and with success, were Castriotto, Marchi, Errard de Bar le Duc, de Ville, and Count de Pagan; but it was Marshal de Vauban (a distinguished general under Louis XIII. and XIV.) who first reduced it to anything like order, and laid down mathematical rules for the direction and proportion of all the lines under all circumstances. plan he proceeded upon was to inclose the place to be fortified within straight lines, forming a polygon, and to treat each line of the polygon as a base of fortification; to be flanked by bastions; the curtain lying between. The length of the side of the polygon under his rules varied from 360 to 500 yards; in order that the whole might be commanded by the artillery in the bastions. De Vauban built no less than thirty-three new fortifications, besides improving no less than 300; and, in the course of so doing, invented three systems, or rather added to his first system, at two successive periods, additional works, with a view to enable the besieged to prolong the defence after a first breach should have been made.

VAUBAN'S FIRST SYSTEM.

Annexed is a diagram of what is termed a front of fortification, upon Vauban's first system, which comprises all the main works common to every front of fortification.

Here 1 1 is the Curtain; 2 2 are the halves of two Bastions, their flanks adjoining and projecting from the curtain, and their faces looking out towards the exterior; the Main Ditch, 3 3 3, runs along bastions and curtain in a continuous line; 4 is the Ravelin, or Demi-Lune, having only two faces (and no flanks), being situate on the exterior side of the main ditch, but having a ditch of its own (5 5), which communicates with the main ditch. Beyond the main ditch and the ravelin ditch, is (6 6 6) the covered way, being a raised ground intended for the movements of the soldiers in the work of defence, and protected by the crest of the glacis (7 7.) which is the outer ground of all, sloping down gradually to the open country, The large spaces in the covered way (6A 6A), are called Places of Arms, for the assembling of the troops: that at the apex is termed the Salient Place of Arms, from its position at the salient angle of the counterscarp; the other two, marked 6a, Re-entering Places of Arms, from being placed in the re-entering angle of the counterscarp; 8 is the Caponnière, a small work, consisting of a double parapet communicating between the gorge or

rear of the ravelin, and the Tenaille (9), a low work in the ditch in front of the curtain and between the flanks of the bastions, serving for the protection of the troops in moving from one place to another, after a breach has been effected in the shoulders of a bastion. The tenaille is only used as the mode of communication with the ravelin when the ditch

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FRONT OF FORTIFICATION UPON VAUBAN'S FIRST SYSTEM.

is a dry one; when it is a wet one, bridges have to be used instead. All within the main ditch is termed the body of the place, or enceinte; the works without the main ditch-the ravelin, covered way, caponnière, tenaille, &c.—are termed outworks. The great principle involved in this system is that all the works mutually protect one another: the fire from the faces of the ravelin scour the country in front of the faces of the bastions, whilst the fire of the faces of the bastions commands the ditch of the ravelin, and the glacis; and that of the flanks thereof commands the main ditch, scouring the approaches to the curtain.

It may here be explained, that all angles projecting outwards from the body of the place are called salient angles; and all angles projecting inwards, towards the body of the place, are called re-entering angles. Thus the two faces of the ravelin form a salient angle; the same with the two faces of the bastion; the same with one of the faces and the adjoining flank of the bastion; but the flank of the bastion, with the curtain, forms a re-entering angle. The whole extent of rampart comprehending the right face and right flank of one bastion, and the left flank and left face of the opposite bastion, and the curtain between them, is termed a front of fortification, or line of defence.

VAUBAN'S SECOND AND THIRD SYSTEMS.

When Vauban introduced the simple system of works for mutual defence, above briefly described, the art of attack was very little improved upon the old method. The artillery was still brought to bear, as heretofore, directly upon the faces of the bastions and ravelins, and pursued the work of attack laboriously and slowly, exposed all the while to the

fire of the besieged, from positions much superior to those temporarily thrown up by themselves. In short, the defence still maintained the superiority against the attack. It was Vauban himself, who, after methodising his first bastion system, devised a system of attack which completely set at defiance all the precautions upon which it was based, and gave the attack a decided superiority. At the siege of Philipbourg, A.D. 1688, this great commander (acting, it is surmised, upon a hint derived from observation of the operations of the Turks at the siege of Candia, some years previously) determined to alter the position of his batteries, placing them at right angles to and opposite the prolongations of the faces of the works; and then so regulating the charge and elevation of his guns, that the shot, instead of striking the battery point blank, should sweep the whole length of the covered-way, and within the pallisade; and, by frequent bounds, dismount the guns, and place the defences hors de combat. This mode of firing is called the ricochet, and is a species of enfilade firing; the only difference being, that in it the charge of powder is considerably less-a half, or even a quarter charge-and the gun a little elevated. So successful was this mode of firing found to be, that a few years afterwards (1697) Vauban, by means of it, took the fortress of Ath-which he had himself constructed, and which he considered his masterpiece-after thirteen days of open trenches, with a loss of only 50 killed and 150 wounded.

It was to counteract this terrible mode of attack that Vauban introduced traverses, or projecting parapets, across the covered-way (to be shown in the next engraving), which had some effect; but not sufficient, by any means, to balance the powers of attack and defence; and the great engineer saw the necessity of resorting to further complications for protecting a portion, at least, of the garrison from the terrible ricochet-fire; and additional works, for defending the enceinte after a breach had been formed in the face, or shoulder of a bastion. In his second system, which he employed at Landau and Befort (1684 and 1688), he separated the bastions from the body of the place by a ditch, about 40 feet wide, in order to enable the latter to make a second defence; and fortified the angles of the bastions by small pentagonal towers of masonry, called tower-bastions, under which were casemates for two guns, &c. In his third system, employed at Neu Brissack (1698) he increased the size of the ravelin, and added to it a redoubt; and also increased the size of the tower-bastions, and altered their arrangement, and that of the casemates.

COEHORN AND CORMONTAIGNE.

Coehorn, who was contemporary with Vauban, introduced some additional variations upon his system, which, however, it is not very important here to particularise, as the best of them are comprised in the modern system, shortly to be noticed. We pass on to Cormontaigne, who, about thirty years after Vauban's death, was the author of some very important changes, the usefulness of which is acknowledged to this day. But, not to particularise each succeeding improver or improvement, we now proceed to give a general sketch of a portion of a fortification, upon what is called

THE MODERN SYSTEM,

That is, the method of Cormontaigne-itself an improvement upon the systems of Vauban, with such additions as modern engineers have thought

it proper to introduce, and which are usually adopted. Some additions to those systems which are only occasionally adopted, we shall, in this description, disregard. The portion here represented comprises two bastions, a ravelin, and two half-ravelins, illustrating the command of the latter over the bastions just spoken of.

The portion a b c d e constitutes a front of principal works, comprising two half-bastions and a curtain, the raised ramparts within which are formed of

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the earth dug out of the main ditch, h h h; g g is the tenaille; ii, the caponnière; jjj, the ravelin; k k k, the ditch of the ravelin; 77, the covered way; m m, the re-entering places of arms in the covered way; nn, redoubts, in order to increase the strength of the covered way, and to facilitate the making of sorties upon the enemy. The descents into the ditch by which these sorties are made, are generally inclined planes, called rampes. Within the ravelin are coupures, or cuts, marked pp, to prevent the enemy taking the redoubt of the re-entering place of arms, before the redoubt of the ravelin itself is taken.

The annexed engraving shows a section of the bastion-rampart across the line a b of preceding engraving:-b c d is the terre-plain of the rampart, upon which are placed the troops and cannon for the defence, and which is generally from 30 to 40 feet broad; within which terre-plain, cm, is the banquette, or step, on which the soldiers stand to fire through the embrasures in the parapet, the height of the latter, d e, being so regulated as to afford sufficient cover for the cannon and men. The superior slope of the parapet, e f, is directed to the edge, t, of the opposite side of the ditch, so as to command the covered way, tw; fi is the exterior slope of the parapet, made of earth, and about equal in height to the width of its base; irp, is the revetment, or wall-facing of the parapet, which is strengthened within at

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