the height of the barbette. The lateral slopes of the bar- conversion of stores of information to the best practical uses. bette and of its ramps should be revetted whenever it is In passing through a country, it requires an experienced possible to obtain sods, fascines, hurdles, or other materials suited for the purpose, in order to economize space in the work, as the base of the slope may be then reduced to one-fourth or one-sixth the height; when unrevetted they have slopes of one-sixth. The terrepleine of the barbette may require, as at C, to be covered in flank by a traverse. The mode of con At any point g of the face AB raise a perpeniicular gh, either 18 or 20 feet in length, to include the amount of recoil; at the point h thus determined raise a perpendicular to gh, and prolong it to its intersection with the other B face AC at E, then setting off AF on the other face equal to AE. the capital AD set off a double perpendicular at any point i, prolonging it both ways, and mak On FIG. 33.-Construction of a Barbette in ing it and il each at least equal to 43 feet to represent the half breadth Fig. 24. In the case of a partly sunken parapet, in which the portion above the banquette is raised above and the portion below the banquette excavated below the plane of site, as in fig. 35, the barbette constructed in the hollow portion will enable the gun to fire over the parapet; and it should be protected by forming a bonnetted embrasure, which may be sometimes made large enough, as here represented, to hold two guns. It need scarcely be added that an engineer ought to be ready to adapt any of the expedients here briefly noticed to the circumstances of the case before him, and that a mind stored with resources against any contingency is the highest endowment of a good officer. It must be obvious that in Field Fortification even a limited knowledge of the art of war opens a wide field for the exercise of the talents and resources of engineers; but the possession of a military coup-d'œil, which comprehends at a glance the true bearing or character of objects and events is necessary for the oye to seize quickly on whatever it presents calculated to prove advantageous or disadvantageous for attack or defence; to appreciate the value of villages, inclosures, and broken ground; to 1 now where to dam up rivers, to scarp heights, to form abattis, trous-de-loup, and other obstacles; to select the best situations for field-forts and redoubts, and the best sites for batteries; and to arrange the defensive measures with reference to the number of troops disposable, so that the movements of the defenders may not be obstructed or retarded, and their communications may be short and easy. The variety of ground upon which military operations must be carried on precludes the possibility of laying down fixed rules in regard to this subject; the accidents of the ground, and the peculiar circumstances of each individual case, must determine the extent and description of the works to be constructed, as well as the obstacles most proper to be formed for retarding the advance of an enemy.1 But though the observance of fixed rules be impracticable, general principles are of universal application; and certain maxins founded upon them hold good in the construction of field-works as much as in the erection of the complicated works of a fortress. These maxims, which are of invariable application, are-(1) that the works to be flanked must never be beyond the range of the projectiles used in the works flanking them, or, in other words, that the length of the lines of defence must never exceed the effective range of the weapons in use; (2) that the angles of defence must be about right angles; (3) that the salient angles of all works must be as obtuse as possible; (4) that the ditches must be efficiently flanked; (5) that the relief of the flanking works must be determined by the length of the lines of defence; and (6) that the works must be constructed with reference not only to the direct and immediate obstacles which they present to the enemy and to the positive effect of their fire on the approaches to them, but also to the support they derive from or afford to other works. Field-works are either open at the gorge as in figs. 36, 37, 38, 39, or inclosed all round as in figs. 40, 41, 42, 43. They are of the following kinds : Redans, or simple heads.... Bastioned heads...... Redoubts Star forts..... fig. 36. 37. 38. 39. 1 Shaw's Course of Field Fortification, p. 9 scq. Much assistance has been derived from this useful work in the compilation of this article, as well as from the admirable treatise on Field Fortification |