Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/451

FORTIFICATION 437 other. The object, therefore, in arranging field works for mutual defence should be so to regulate their reliefs that the lines of defence should terminate at such distance from the ground as to give effective defence to the parts of the works intended to be flanked. The Redan may be considered the most simple form of defensive work, though a straight parapet terminating by short returns at each flank, in the form either of epaulements or of regular para pets, may occasionally be combined with defensive works. The redan is open in the rear, and the line joining B and C is called the gorge. The " Lunette" is a redan to which flanks or lateral wings have been added; in form, therefore, it resembles a bastion. In fig. 48 Lunettes are shown so arranged that the faces of those in rear may flank the faces of those in front; but with respect to the distribution and arrangement of the works destined to form Lines of Intrenchment more will be said hereafter. The " Tenaille" is the reverse of the redan; it consists of two lines forming a re-entering angle facing the exterior. It can, from its form, only be used in direct or approximate connection with other works which close up or cover the ends of its lines. Either alone or combined with redans it is very commonly used in continued Lines of Intrench- ments. Fig. 44 represents a Line of Redans joined by straight lines, and fig. 45 a Line of Irregular Tenailles, whilst fig. 52 represents a normal line of Tenailles, of which the FIG. 52. Teiiailles. re-entering angles do not exceed 100, and the sides are equal, and fig. 53, an arrangement of Teuailles, with irre gular sides, by which a Redan, as DEF, is interposed be- Fio. 53. Combined Tenailles and Redans. tween every pair of Tenailles. The Line en cremaillere (fig. 46) is also derived from a combination of irregular ten- ailles, and is in many circumstances a very satisfactory arrangement. In selecting between these and other arrangements, including the bastion trace (fig. 47), the engineer must be guided by the nature of the ground and the special objects to be attained. A slight consideration is sufficient to show that the combination of regular tenailles in fig. 52 is only applicable to ground in itself regular. In most cases, however, the ground will be more or less irre gular, and the works to defend it must be so also. When it is necessary to approach close to the bank of a river or a ravine, the Cre maillere Line (fig. 49) is the simplest and best, the short or flanking sides being so placed as to face the probable direction of approach, and next to that the combined Redan and Teuaille. Of open works, Lunettes admit of the most scientific arrangement, as they can be so placed in lines with intervals as reciprocally to flank each other, and thus to form a line of defence very similar to a regular bastion ed line. The employment, however, of works open at the gorge must be restricted to positions where the enemy can only approach in front, his approach in other directions having been rendered impossible by obstacles or by other works. In every case it is desirable to take ad vantage of peculiarities in the features of the country, and to modify them into such obstacles as shall relieve the de fenders from apprehension of danger, and leave them at liberty to direct their attention more exclusively to the weaker points of their position ; but in no case should even apparently inaccessible points be left unwatchecl, as an en terprising and skilful adversary will at times surmount difficulties which had appeared insurmountable. As nat urally defended points in a position can only be looked upon as exceptional advantages, it is evident that works left open at their gorges would be liable to surprise, and would therefore prove but imperfect instruments of defence. On this account it has been not unfrequently pre scribed that such works should be left unclosed when with in range of musketry fire from the defences behind them ; but it is better to lay down the fixed principle that in all cases they should be closed at the gorge, as the power of driving an enemy out of the interior of such a work is of little value, for his object would be not to remain in its interior, but to turn its parapet to his own uses. The manner in which they are generally closed is shown in fig. 54, which is a lunette secured at its gorge by a loop- holed stockade, an obstacle effective against an enemy, FIG. 54. Lunette closed at the Gorge. and, at the same time, easy of destruction, should he suc ceed in temporarily obtaining possession of the work. Any of the obstacles previously described, such as abattis, <kc., may be used for the same purpose, but they have the dis advantage of not covering the defenders of the work from the enemy s fire. An engineer in deciding between open works, such as have been described, and closed works such as will now be described, ought to take into consideration the circumstances of ground not only as affecting the security of the work itself, but as affecting the ease or difficulty with which support can at any moment be afforded to its garrison. Open works are not fitted for any position where they are likely to be left to their own resources, even for a short time, as small bodies of men cannot be expected to stand firm against a vigorous attack from a superior force, unless satisfied that support is at hand. Closed works, therefore, in which the parapet is continuous on all sides, can alone be relied upon under such circumstances ; and the nature of the obstructions adopted in their construction should be such as to afford the garrison a reasonable con fidence that by a vigorous defence they may be able to hold the enemy at bay ; for no general should expect to find in soldiers, as a body, that heroism which leads to self-sacrifice without hope. The easy capture of the the redoubts at Balaclava, garrisoned by the Turks, is an illustration of this principle ; for though it is possible that they might have been longer maintained by French or British soldiers, it would have been unreasonable to expect that their defenders should remain firm until overpowere I and cut down by their assailants, which must have been the result had not a supporting force been at hand to ro-