The most perfect fortification for defending a line of country pre senting few natural obstacles to the advance of an enemy, should the importance of the position render it advisable to incur the labour of the construction, would be a series of bastions connected by curtains, either straight or broken. The principles on which the several fronts of fortification should be formed correspond to those adopted for regular fortresses, which are described in the article FORTIFICATION ; the only difference being in the lengths of the several parts. These depend upon the whole length of the front, which here should not exceed 180 yards, that the ditches of the bastions may be well defended by common muskets from the collateral flanks. Neither ravelin nor covered-way would of course be necessary.
Lines of intrenchment composed of works placed at intervals from one another, provided the distances be not so great as to prevent the troops in them from mutually assisting each other, have great ad vantages over those formed of continuous lines of parapet. In the latter case it is scarcely possible for the army to make a movement for the purpose of attacking the enemy however favourable the oppor tunity, since much time would be lost in issuing from the line through the narrow passages ; and as these are the objects against which the fires from the enemy's batteries would then be incessantly directed, it would be almost impossible to form any extended front for attack ; besides which, the enemy penetrating at any one point the whole line is turned. Detached works, on the other hand, constitute a number of strong points by which the position of the army is secured; while through the spacious intervals an advance or retreat may take place with the utmost facility. Their artillery is conveniently situated for putting the enemy's line in disorder previously to the attack, and for protecting the retiring columns in the event of their quitting the field. It may be added that detached works are capable of being easily adapted to any kind of ground ; for it is merely necessary to place them ou the more elevated spots in such situations that the enemy may not be able to penetrate between them without being exposed to their fire.
On level ground the intrenchment may consist of a number of redans, as A, It, c, with or without flanks, disposed on a right line or curve, and at distances from one another equal to about 300 yards, that the fire of musketry from them may defend the intervals. In the rear, and opposite the intervals between the works in the first line, a second line of works as 6, E, should be formed; and the faces of these should be disposed so as to flank the ditches and approaches to the others. The gorges of the exterior works should be open, as in the figure, or only protected by a line of palisades, which, in the event of the enemy gaining possession of those works, might be destroyed by the artillery in the second line.
Instead of a series of redoubts forming an interior line, it may suffice, should the works A, B, C, &c., be disposed on a convex arc, to have one large central redoubt as F, so situated as by its artillery to defend both the intervals between the redans and the ground within their line.
All the works which have been described consist of parapets formed of earth obtained by cutting a ditch in front; and the profile of any one work with its ditch is shown in the subjoined figure (4).
The elevation of the crest A above the natural ground is about 74 feet, unless the vicinity of a commanding height in front should render a greater relief necessary, and the depth of the ditch may be the same. The thickness A a of the upper part of the parapet is variable, and depends upon the importance of the work, or rather, upon the arm which may be employed in the attack : if it were required only to resist a fire of musketry, 3 feet would suffice ; but from 8 feet to 12 feet would be necessary in the event of artillery being brought against it. (Twelve-pounder shot is the heaviest which the French have ever yet employed in the field.) The form of the parapet is the same as in permanent fortification ; when time permits, the exterior and interior slopes should be revbted with sods, .an4 a line of palisades should be planted along the foot of the counterscarp.
Ll NIN, a crystalline substance of unknown composition found in the mountain flax (Linum catharticum).