zd bisecting the exterior angle ABC is the capital of the bastion.
xy is the perpendicular, the proportionate length of which to the exterior side BC (usually about one-sixth) is an important element of the trace.
efC is the angle of defence.
BCf is the diminished angle.
cde is the flanked angle or salient angle of the bastion.
e is the shoulder of the bastion.
def is the angle of the shoulder.
efg is the angle of the flank.
The line of the escarp is called the magistral line since it regulates the trace. When plans of fortifications are given without much detail, this line, with that of the counterscarp and the crest of the parapet, are often the only ones shown,—the crest of the parapet, as being the most important line, whence the fire proceeds, being usually emphasized by a thick black line.
| Fig. 20. |