Here was therefore the parting of the ways. For those who objected to casemate fire, the bastioned trace was the way of salvation. They were soon in the majority; perhaps because the symmetry and completeness of the idea captivated the imagination. At all events the bastioned trace, once fairly developed, held the field in one form or another practically without a rival until near the end of the 18th century. The Italian engineers, who were supreme throughout most of the 16th century, started it; the French, who took the lead in the following century, developed it, and officially never deserted it until late in the 19th century, when the increasing power of artillery made enceintes of secondary importance.
It will be useful at this point to go forward a little, with a couple of explanatory figures, in order to get a grasp of the component parts of the bastioned trace as ultimately developed, and of its outworks.
In fig. 19 ABCD represents part of an imaginary line drawn round the place to be fortified, forming a polygon, regular or irregular.
ABC is an _exterior angle_ or angle of the polygon.
_abcdefghijk_ is the trace of the _enceinte_.
(Two demi-bastions with the connecting curtain make the bastioned front, _defghi_.)
_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.
_cde_ is the _flanked angle_ or _salient angle_ of the bastion.
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, reproduced from a French engraving of 1705, shows an imaginary place fortified as a hexagon with bastions and all the different kinds of outworks then in use. The following is the explanation of its figuring and lettering.
1. _Flat bastion:_ Placed in the middle of a curtain when the lines of defence were too long for musketry range.