The Counterscarp (b) is the wall, or slope of the ditch, opposite to the escarp.

The Faces of a work (p q) are those parts which form a salient angle, projecting towards the country.

The Flank (q G) is the part of a work so disposed as to defend another; joining the face of a bastion to the curtain, &c.

The Bastion (ML) is a work composed of two faces, and two flanks. Bastions are joined by curtains, and are constructed salient, and with flanks, in order that the whole escarp may be seen, and that a reciprocal defence may be obtained.

Bastions are of various kinds-viz., full (M), empty (L), also flat, detached, demi, and tower bastions.

A Full bastion (M) is when the terreplein occupies all the interior space of the bastion. From the description of this bastion, that of all the others may be ascertained.

The Curtain (G RH) is that part of the rampart which lies between two bastions, and joins the flanks thereof.

A Front of fortification consists of two half bastions, and a curtain.

The Ditch (B) is an excavation from 12 to 24 feet deep, and from 90 to 150 feet broad, surrounding the rampart. The side of the ditch nearest the place forms the escarp (a); and the opposite part, the counterscarp (b) is made circular opposite to the salient angles of the works.

The Covered way (V) is a space of about 30 feet broad, extending round the counterscarp of the ditch, being covered by a parapet from 7 to 9 feet high, with a banquette.

The Glacis (X) is the superior part of the parapet of the covered way, forming a gentle slope towards the country, and terminating at from 120 to 180 feet; it covers the revetment of the body of the place.

The Places of arms of the covered way are spaces contrived in the salient, and re-entering angles of it; those (c) in the reentering angles flank the branches of it, and contain troops for sallies, and its defence; and those (P) in the salient angles serve for assembling the Troops destined for the defence of the covered way.

The Sally ports are openings cut in the glacis, at the faces of the re-entering places of arms, and at the branches of the covered way. They are used in making sallies from the covered way.

The Traverses (n) in the covered way, are parapets which cross the breadth of it at the salient, and re-entering places of arms, &c. They cover the troops who are drawn up behind the parapet of the covered way, from the enfilade fire of the enemy. There are passages cut in the parapet of the covered way, close to the traverses, in order to form a communication from one part of the covered way to another: these passages are about 6 feet wide, and are provided with gates.

A Citadel is a fortress joined to the works of a place, and is

fortified both towards the town, and country. It should always be situated on the most commanding ground, serving to keep the inhabitants in awe, and, should the town be taken, it becomes a retreat for the garrison.

The Esplanade is a space of even ground, clear of buildings, situated between the town, and citadel.

The Body of the place (or Enceinte) consists of the works next to, and surrounding the town, in the form of a polygon, whether regular or irregular.

Outworks are those works which are constructed beyond the body of the place, such as tenailles, ravelins, &c.

The Tenaille (D) consists of two faces, and a small curtain. It is constructed between the flanks of the bastions in front of the curtain, and has a terreplein, parapet, and banquette.

The Ravelin (P) is constructed opposite the curtain, (in front of the tenaille,) is composed of two faces, which form a salient angle towards the country, and of two demi-gorges formed by the counterscarp.

A Horn-work is composed of two half bastions, and a curtain, with two long sides directed upon the faces of the bastions, or ravelins, so as to be defended from them.

A Crown-work is composed of a bastion between two curtains, which are terminated by half bastions. It is joined to the body of the place by two long sides.

Lunettes, and Tenaillons are works constructed on each side of ravelins, consisting of two faces.

It con

A Fleche, or Arrow, is constructed along the foot of the glacis before the re-entering, and salient places of arms. sists of a parapet, whose faces form a salient angle, and are about 120 feet long, and it has a communication with the covered way, cut through the glacis.

The Caponiere (Y) is a work intended to cover a passage across the ditch. That from the tenaille to the gorge of the ravelin is a road about 30 feet wide, covered on each side by a parapet 7 feet high, its superior slope terminating in a glacis about 60 feet wide.

A Cunette is a small ditch made in the middle of a dry ditch, to drain off the water from the place, &c.

A Batardeau (e) is a solid piece of masonry, 7 or 8 feet thick, crossing the whole breadth of the ditch opposite the flanked angles of the bastions. It retains the water in those parts of the ditch which require to be inundated.

A Ramp (t) is a road cut in the interior slope of the rampart, forming a communication from the town, &c., to the terreplein.

A Cavalier is a work constructed upon the terreplein of a full bastion, being from 8 to 12 feet above the rampart, with a parapet 6 feet high. Its use is to command some rising ground within cannon-shot, and to serve as a traverse for preventing the neighbouring curtains from being enfiladed.

Parallels, or Places of arms, thrown up at sieges, are trenches formed to connect together the several approaches to a besieged place.

Zig-zags, or Boyeaux of communication, are trenches made for the approaches from the parallels to the besieged place. They are generally 3 feet deep, and have a parapet, and banquette.

A Redan consists of two faces forming a salient angle (which should not be less than 60°) with parapet, &c. (Vide FIELD FORTIFICATION.)

A Lunette (Vide FIELD FORTIFICATION) has two faces, similar to the redan, and also two flanks.

A Redoubt is a square, polygonal, or circular field fort.

A Star fort consists of a succession of salient and re-entering angles, formed on the sides of a polygon. These forts are usually constructed on a triangle (when they have six salient points), or a square (having eight salient points). (Vide FIELD FORTIFICATION.) Tetes de pont, or Bridge heads, consist of redans, &c., which are constructed the banks of rivers, to protect the passage across them. (Vide FIELD FORTIFICATION.)

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Lines are formed for the entrenchment of armies, and are composed of a succession of redans, &c., joined by curtains, which should not be more than 120 yards distant from each other, to afford mutual protection, and defence. (Vide FIELD FORTIFICATION.) An Epaulment is an elevation of earth thrown up to cover troops from a flanking fire.

Loop-holes are oblong holes, from 15 to 18 inches long, six inches wide within, and two or three without. They are cut through timber, or masonry, for the service of small arms.

Palisades are stakes of strong wood, 8 or 9 feet long, and 6 inches thick, fixed about 3 feet in the ground, and 3 or 4 inches asunder.

Fraises are a kind of palisades, placed horizontally, or obliquely in the exterior slope of ramparts.

Chevaux de frise consist of a piece of timber from 9 to 12 feet long, and about 6 inches in diameter, into which staves are inserted crossways, about nine inches asunder, about two inches thick, six feet long, and pointed at the end, if not shod with iron. Their use is to stop up a breach, defend a passage, or form an entrenchment against cavalry. Chevaux de frise are sometimes made entirely of iron.

Abattis consist of trees with their branches shortened, and sharpened at the ends; they are used instead of chevaux de frise on an emergency.

Hurdles are about 3 feet high, and 2 broad, and are used in sieges to stop up breaches, &c.

Trous de loup are holes dug in the ground in the form of an inverted cone, about 6 feet deep, and 44 in diameter at the top, having a picket fixed in the centre of the bottom, 6 feet long, and 4 or 6 inches square, the point being on a level with the upper sur

face of the ground. These pits are used to prevent the approach of bodies of cavalry.

PERMANENT FORTIFICATION.

Remarks, and general rules.

The ground plan, and relief of bastioned fortifications are mutually dependent on each other; and, as a variety of causes occur to influence both according to the various sites occupied, it is impossible to give them any fixed arrangement, and dimensions, applicable under all circumstances. However, under the supposition that the site to be fortified is a horizontal plane, a great number, and variety of systems have been proposed at different times; almost every author, who has treated of fortification, having invented one, at least, of his own. Notwithstanding this diversity of opinion, as to the best system, all agree that the following general principles should not be lost sight of in the construction of fortifications.

1. Salient angles should be as large as possible, and never less than 60°. The larger they are the smaller will be the space in front undefended by direct fire. If less than 60°, the salients of earth are too acute to stand firmly for any length of time; and the angles of masonry are easily damaged; besides which the space within the parapets becomes too restricted to admit of a gun being worked near the angle.

2. Angles of defence should be right angles, or slightly obtuse. If less than right angles, the fire from the flanking works might injure the defenders of the works they flank; as troops generally, and more particularly at night, fire in a direction perpendicular to the parapet; and if too obtuse the fire might be directed wide of its object. Besides, embrasures should be cut as direct as possible; as the more they are oblique, the more they weaken the parapet.

3. The length of the lines of defence shall be such, that the works defended may be within the effective range of the projectiles used.

4. The works should be so disposed that the assailants may not be able to obtain cover in any part of the exterior, within range of the projectiles of the defenders.

5. The escarps of the body of the place should be of such height, or construction, as to be secure against escalade.

6. The masonry should be sufficiently covered from the view of the enemy, to prevent his making a practicable breach from a distance.

7. The interior of every work should be completely covered from the view of an enemy outside it; so that he may not be able to fire directly into any part of it. Interior works should therefore have a command over those in front of them, at least equal to the height which a besieger can give to the parapets of his lodgments, and which is seldom less than 3 feet.

8. Every opportunity should be seized of so directing the faces of works that an enemy may not have it in his power to enfilade them by ricochet fire.

9. In the general construction of fortifications the salients should be few, and sufficiently prominent to force the besieger to take them before he can attack the re-entering parts. The object of this is to reduce the number of points of attack, as, the fewer they are, the less advantage an assailant derives from his numerical superiority.

10. Permanent fortifications must be considered very incomplete without a sufficiency of casemated cover for the sick, and wounded, and for the portion of the garrison off duty. The magazines of ammunition and provisions, should also be secure from the effects of shells; and the supply of water ample, and certain.

11. Small enclosed works, in which the defenders must be crowded, without cover from vertical fire, should never be employed in permanent fortification. The strength they impart can never make up for the loss the garrison must suffer by them.

12. Outworks, and detached works should have easy communications with the main work, to admit of their garrisons receiving reinforcements, or supplies, when necessary; and to enable them to retreat, when the works are no longer tenable.

13. Every inclosed defensive work of importance should, if possible, be provided with a keep, or citadel, or interior retrenchment, to which the garrison may retire when the main inclosure (or enceinte) is forced.

14. Outworks, and detached works near the body of the place, should be so constructed that the enemy, when he has taken them, may not be able to use them as defensive works.

15. Outworks, and detached works, should always be of sufficient strength to force the enemy to make regular attacks on them. Advanced works of a weak construction are likely to do more harm than good; for the troops of the garrison seeing them taken with comparative facility, would naturally lose confidence in the strength of their remaining defences, while that of the assailants would be increased by early success.

16. All fortifications should be provided with means of egress, and ingress, to enable the garrison to assume the offensive, whenever opportunities offer; and to admit reinforcements into the fortress.

17. There are very few fortified places that agree with any published system, though some resemble one or other of the systems, or consist of combinations, or modifications of them. The systems which have been wholly, or partly carried into execution are, of course, the most interesting, and form valuable subjects of study. A knowledge of their advantages, and defects, and the best methods of attacking, and defending them, will enable the military student properly to appreciate works which have been, or are to be constructed; and the operations by which fortresses have been, or may be captured.