The Curtain (G R H) 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 re-entering 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.