Bastion
a projecting mass of earth or masonry at the angle of a fortification, having two faces and two flanks, and so constructed that every part of it may be defended by the flank fire of some other part of the fort. The flanks of adjacent bastions are connected by a curtain. The distance between two such flanks is termed the gorge. A detached bastion is called a lunette. Also: (a) A composed bastion is one which has two sides of the interior polygon very irregular, with the effect of making the gorges also irregular. (b) A cut bastion is one which has a re-entering angle instead of a point. (c) A deformed bastion is one in which the irregularity of the lines and angles prevents the structure from having a regular form. (d) A demibastion is a bastion composed of one face only, with but a single flank and a demigorge. (e) A double bastion is a bastion raised on the plane of another one. (f) A flat bastion is one erected in the middle of a curtain when the latter is too long to be protected by the bastions at its ends. (g) A hollow bastion is one hollow in the interior. (h) A regular bastion is one so planned as to possess the true proportion of its faces, flanks, and gorges. (i) A solid bastion is one solid throughout its entire structure.