deduced from these works. The characteristic of both is a polygonal enceinte, flanked by small casemated towers, or bastionettes, and these covered by detached bastions. At New Brisac, (3d system,) Vauban also greatly enlarged both bastion and ravelin, placing a strong redoubt, or inner work, in the latter.

After Vauban, the next great engineer who devoted himself to the advancement of the art, was Cormontaingne.*

What is usually taught under the name of the Modern System is mainly based on the improvements of Cormontaingne, modified by subsequent French engineers. Its main features of difference from the first trace of Vauban are,

1st, The enlargement of the bastions, affording more space for artillery, musketry, the defence of breaches, and the construction of retrenchments on those works which are at once the most active in defence and the most liable to attack.

2d, The great salience and capacity of the ravelins, compelling the attack and capture of those works before the crowning of the covered-way in front of the bastion can be accomplished. This is not necessarily the case in Vauban's system, where the salients of bastion and ravelin are nearly included in the circumference of the same circle. Vauban's ravelin compels the besieger to use more means, for it must be reduced; but this need not be till all is ready for the attack of the bastion also, and therefore it adds little or nothing to the duration of the siege. In the modern system, also, the ravelin completely covers the shoulders of the bastions from batteries. on the glacis before it. In Vauban, these batteries can breach the bastion so near the shoulder that the flanks are thrown open to enfilade. The salience of the ravelins, likewise, compels the besieger to open his first parallel at a distance too great for the effective ricochet of the faces of the bastions, and gives great protection to sorties.

3d, The ample size of the ravelins admits of the construction of redoubts within them, which must also fall before the bastion can be carried, their flanks bearing in reverse fire upon the breaches.

* See NOTE V, Cormontaingne.

triangular portion is cut from the interior of the redoubt, and added to the ditch of the ravelin.

The trace of the re-entering place of arms is circular. The arc is described from the original angle of the counterscarp formed by the ditches before ravelin and bastion as a centre, passing through a point on the capital of the redoubt, 20 yards beyond the counterscarp.

Traverses at each intersection of this arc with the outer edge of the covered-way complete the enclosure of the places of arms. There are three more traverses on each branch of the covered-way of the ravelin, the outermost terminating on the prolongations of the faces of that work. These last traverses have superior slopes of only 9 feet; those adjoining the place of arms being 18. The passages round the traverses are en cremaillère, or indented. The breadth of the glacis is 60 yards. At the salient place of arms before the ravelin, the angle of the crest of the glacis is cut off by a line 9 yards long at right angles to the capital.

There is a coupure, or retrenchment-cut, across the rampart of each face of the ravelin. It consists of a parapet, and a ditch 6 yards wide, the counterscarp of which is determined by a perpendicular to the face of the ravelin drawn from the extremity of the escarp of the redoubt in the place of

arms.

The principal advantages sought by this trace have been already pointed out. A few of the minor peculiarities may be noticed. The trouée of the Tenaille, being masqued by the spread of the ravelin, the ends of the Tenaille may be removed to a safer distance, as regards splinters, &c., from the flanks, without fear of exposing the curtain to the enemy's lodgments on the glacis. The small flanks given to the parapet of this work serve to bring a musketry fire directly on an enemy entering the main ditch from that of the ravelin.

The ravelin being traced as an equilateral triangle has an opening of 60° only, the most acute which is permitted by the rules of experience. When several fronts of this system are in one ine, this great salience of the ravelins completely covers the faces of the bastions from enfilade.

The ditches of the ravelin and its redoubt are both flanked by the face of the bastion, whilst the flanks of the redoubt bear directly on that part of the bastion, between the salient and the prolongation of the face of the ravelin, which is most liable to be breached. These flanks are intended to have guns in casemates, which would be completely protected till the fall of the redoubt itself.

By the construction of the redoubt in the place of arms, the ditch, on one face at least, is quite defiladed; the small flank bears directly on the usual site of a breach in the ravelin; and by the direction given to its demi-gorge on the side of the ravelin, the gorge communication is concealed from the enemy's lodgment before the salient of the ravelin.

The circular trace of the places of arms renders their banquettes less liable to enfilade.

The reduced thickness of the advanced traverses in the covered-way is sufficient to stop ricochet shot, but not to resist the direct artillery fire of the enceinte, should a besieger take advantage of their cover.

The coupure in the ravelin is intended to prevent the assailant from driving the garrison out of the redoubt in the place of arms, as soon as he captures the ravelin; and its ditch is so traced as to be defiladed by the parapet of the redoubt. It must be confessed that the former more important object seems, in the trace laid down, to have been somewhat sacrificed to the latter.

A difference of 8 feet between the level of the main ditch and the ditch of the ravelin serves to bring a greater part of the latter into view from the face of the bastion,* covers the communication with the place of arms, and is an obstacle to sapping towards the bastion.

The dimensions of parapets, &c., may be drawn the same as

* "I have heard General Filley relate that, at an attack which he conducted during the war in Flanders, between 1744 and 1748, he placed several companies of grenadiers in the ditch of a Ravelin, to wait the moment of assault; and that there they were entirely sheltered from the fire of the place, heavy as it was."-BOUSMARD, Sup., Book ii.

and should be unnecessary if a fair use has been made of mortars and howitzers from the advanced parallels.

The covered-way being cleared, the sap advances to the crest of the glacis; when, branching right and left, a lodgment is excavated embracing the contour of the glacis before the whole of the attacked faces. This is called the crowning of the covered-way. As the fire of the gun-batteries in the rear has in these latter operations become hazardous to the advanced guard and working-parties, vertical fire must be mainly depended on for preventing the revival of active resistance from the ramparts of the place. Marksmen, too, will be planted behind loopholes of sand-bags in the crowning lodgment, to keep a constant watch on the enemy's embrasures and parapets. Meantime, embrasures are cut through the parapet of the lodgment for the establishment of breaching batteries (Nos. 8, 9, 10, 11, 12,) against bastions and ravelins. Counter-batteries, also, (Nos. 13, 14,) must be constructed at the salient place of arms before the attacked bastion, to destroy the flanks which bear upon its faces, as they, from their situation and shortness, have been less liable to enfilade, whilst, as long as they retain any capacity of action, the storm of the breaches would be very perilous.

Whilst these batteries are being constructed, and are performing their work of demolition, galleries of descent into the ditch are excavated by miners, or ramps formed by blowing in the counterscarp with gunpowder.

Where the remaining defences consist of bastion and ravelin without interior retrenchments or redoubts, the ravelin would be taken by the regular advance of the sap across the ditch, and establishment of a lodgment by sappers on the breach, under a redoubled vivacity of fire from the trenches on the crest of the glacis. The breach or breaches in the bastion would then be stormed. Should there be an interior retrenchment with revetments, the sap must advance up the breach, and a battery be established on the rampart for its reduction.

It is to be noted that, in Vauban's system, any retrenchment within the bastion may be turned by establishing a battery (as No. 15) to breach the curtain through the trouée of the tenaille.

The tenaille itself affords little active defence, and it is not necessary to occupy it.