LINES OF INTRE.*CIIMENT. In the article ENCAMPMENT It has been stated that armies is the field are not now, as formerly, serrounded by fortifications cat:whiting of a continuous line et works; and that, in general, a few breastworks or redoubts merely are con structed at intervals for the defence of the position. It will be suffi cient, therefore, leaving out the consideration of those means of defence which are afforded by the natural obstacles of the country, as escarp ments, rivers, marshes, &c., to describe briefly the nature of those intrenchmenta which were once, in all circumstances, considered indis pensable, and which are still, to a certain extent, necessary when an army is to remain strictly on the defensive.
In the first place it may be said that a continuous breastwork would be advantageous for the protection of portions of a frontier, when the absence of natural obstacles might favour tho enemy's marauding parties in making inroads for the purpose of levying contributions or laying waste the country ; a parapet a n, broken by the redans c, c, from whence the defenders may annoy the enemy in flank on his approach, termed a Redan Line, is the simplest form. The distances of the redans from one another may bo about 150 yards, or not ex ceeding the range of musket shot : such was the construction recom mended by Vauban, and since his time, it has been modified occasion ally by giving to the curtains the form indicated by the lines a c, L c, in order that the ditch might be more effectually defended from the faces of the redans. All the faces should be so disposed that, if pro duced to an extent equal to the range of artillery, the lines of direction may fall on ground where the enemy could not establish batteries for the purpose of enfilading them ; since, in the event of such enfilading taking place, the defenders would be compelled to abandon tho para pets; artillery, if placed there, would be dismounted ; the palisades in the (lath would to destroyed; and little resistance could be made, should the enemy subsequently assault the line. In general the
redans may have the form of equilateral triangles, and the lengths of their sides may be about 50 yards. The eutrauces are usually in the middle of the curtains.
Instead of simple realms the advanced parts of the line have occa sionally been formed of works resembling two united together, as D; which by the French engineers are called queues d'hyrondes, or double reclaims.
Again, when the nature of the ground does not permit the intrench meet to be formed with points so far advanced as tho vertices of the redans c, c ; when, for example, it is required to follow a bank of a river or one side of a road, it is proposed, in preference to a simple straight or curved line, to form the parapet with a series of branches in the positions Indicated by a 6, c d, &e., to P. A line of this kind is said to be it cremailliMrs : and in such situations a succession of fires from the branches a 6, c d, &c., may be directed .ngsinst the enemy during his advance ; on a level plain however the longer branches would be subject to the serious defect of being easily enfiladed. The distances between the salient points b, d, &c., should not exceed 100 yards, and the lengths of the short branches may be about 18 or 20 yards. The re-entering angles a, e, &c., should contain about 100 degreea; and the entrances are usually placed at those points.
A like construction may be adopted when it is required to coffnect two points, as m and N, by a line along a narrow and elevated ridge of ground ; and in this case the directions of the branches b c, d e, &c., may change in the middle of the line, as shown in the figure, in order that the fire from the long branches may be directed to the front of the nearest works, as M and N, in which it is to be supposed that artillery would be placed for the purpose of defending the ground before the intermediate line.
It may be added also, that the line a crentailliares (indented line) is convenient when it is required to join forts on hills or rising ground.