CONSTRUCTION OF FORTIFIED PLACES.
fortified place is in the form of a polygon, more or less regular according to circumstances. The sides of this polygon may be considered as chords of the arches of a cir cle described about the place, and on the relative length of these chords the strength of the place may, in particular cases, very much depend. The lines which form the plan of the fortification, as described on the ground or on paper, are called the trace, and the height to which it is carried, the relief In Plate CCLVII. Fig. 1, is exhibited the trace of a re gular fortification of five sides, in which DEFGH is called the exterior, and KLM NI the interior polygon. The dis tance from A to the angle of toe exterior polygon is called the great radius, and from A to the angle of the interior po lygon the small radius. The part contained between two radii, as EBCF, is called a front of the fortification ; and a line dividing any of the works into two equal parts, as AE, a capital line. The fronts of fortifications consist of bas tions and curtains. A bastion is the part about the angle of the polygon, as VUFZC. The curtain is that part of the front which joins the bastions, as BC In the bastion VUFZC, the lines VU. ZC, are called the flanks ; and UF, FZ, the faces. Bastions which have no flanks, but have their faces produced till they meet the curtain, are called redans This difference gives rise to the two me thods of fortification ; the Bastion system, and the system of Tenailles, or perpendicular fortification.
When an angle is turned from the place, as F, it is called a saliant angle, and re-entering when turned towards the place. as C. The angle F is called the saliant, or flanked angle of the bastion. U, Z, the angles of the shoulder ; and V, C, the angles of the flanks, or re-entering angles. In redans, the angle formed by the face and the curtain is called the flanking angle, or angle of the tenaille. When the shoulders of the bastion are built in the circular form P, Q, they are called orillons, or tours creases. The dis tance between the angles of the flanks. as VC, is called
the gorge of the bastion ; and CM, or AI V, the demi-gorge. A straight line, drawn front the saliant angle of one bastion to the angle of the flank in another, as FB, is called a line of defence. If this line be drawn along the face, and pa rallel to it, it is called a razing defence ; and if the line make an angle with the face, the defence is said to be fichant, or oblique. When the line of defence meets the curtain short of the extremity, the part of the curtain be tween that point and the extremity is called the second flank.
The whole circumference of the works about a town, as represented in Fig. 1, is called the enciente, or corps de la place. Other works have each a particular name; but they are in general called outworks. The chief strength of the corps de la place, as m ell as of the outworks, is a mound of earth called the rampart, and of which the trace shows the thickness at the bottom. On the top of the ram part is raised another mound, called the parapet, for the purpose of covering the besieged and their guns from the fire of the enemy. Behind this, are two or three steps called banquettes, on which the soldiers stand when they fire over the parapet ; and between these and the town, is a passage called the terre-Idein, of sufficient breadth for the movement of troops, and the conveyance of cavalry from one place to another. The rampart is generally lined with a wail, called a revetement, olt the top of which is a pas sage round the parapet of about two feet in bi eadth, called the way of rounds. The slopiag surf ice of a woe k is called the escarpr, from the place ; and if it inclines towards it, the counterscarpe.
Before the rampart in all works, is a ditch called the fosse, made by excavating the ear h for the rampart. Round the counterscarpe of this ditch, and at a convenient distance from it, is cut out a passage called chemincouvert, or the covered-way. From the parapet that defends this, the ground declines by a gentle slope towards the field, and is called the glacis.