It is admitted among military men that in firing over a parapet, the soldier doing the duty as rapidly as poesible, and fearing to expose himself while adjusting his musket, places the latter mechanically in a direction nearly perpendicular to the line of the face behind which he is stationed. It follows that in front of every salient angle of the work there must be an undefended sectoral space, as in a in the sub joined cut, which represents the plan of a square redout, In which trace, in order to avoid the direct fire from the faces, the enemy may advance to the attack ; and on this account it is recommended that the faces of the work should be disposed so that the angles may be turned towards ground which is impassable, or which will not permit the enemy to establish batteries for the purpose of enfilading those faces. When this disposition is not possible, various methods may be adopted by which the troops who man the work might direct some of their fire within those sectors. The simplest of these, and that which is generally put in practice, is to form the crest of the parapet near the angle, perpendicularly to the capital (the line bisecting the angle) as at a b ; by which means the apace between to and z may be directly defended, and the sectors x to and z y being small, very little attention on the part of the men about a and 6 will enable them to give their muskets an oblique direction so as to fire upon an enemy advancing within those spaces. A second method is that of rounding off the interior of the parapet at the angles, as at c d; but this has been objected to on account of the divergency of the lines of fire. The third method, which is much dwelt on by writers on fortificatiou, consists in forming the interior of the parapet with indentations, as at e g and f h, alternately parallel and perpendicular to the capital, each indent being three feet long; and a parapet of this kind is mid to be en crentoilMre. It is evident that by placing men contiguously to the sides of these indentations, a fire may be kept up in either of the directions just mentioned ; and by placing them at the angles, they may fire perpendicularly to the general face of the work. It must be observed, however, that the men cannot fire in these different direc tions at the same time, because, the muskets crossing one another, that of one man might be injured by the fire of the next, and therefore what is gained in one direction is lost in another. The only objections to this method are, that the parapet can be so formed only by man belonging to the corps of Royal Engineers, who are regularly trained to the construction of fortifications, but who may not be present when wanted ; and that the unsteadiness of the soldiers in firing almost always renders such precision.in the formation of the work useless.
The ditch of a redout having no flanks, being unseen and incapable of defence from the parapets, it has been proposed, in order to lave some means of annoying the enemy when in the ditch, to form an enclosed rpaoe A, at one or more of the angles of the ditch, by planting a line of palisades across the latter on two contiguous faces of the work ; the enclosure may have a roof of timber covered with earth, and loop holes, three feet asunder, must be cut in thb palisades, that the defenders may be enabled to fire along the ditches.
Another method, which may be advantageously adopted when a face of the work has considerable length, is to form, as at a, what is called a palisade caponnibre, by planting across the ditch, at the middle of the face, two rows of palisades about eight feet asunder ; each row being pierced with loop-holes. The entrance into the eaponniare is by steps in the interior of the redout and a gallery under its parapet ; and this work, as well as that at a, may have a roof, but in no ease should such roof be above the level of the natural ground, in order that it may be concealed as long as possible from tho view of the enemy. And if
practicable, the floor; of the caponnibre may be sunk, so that the roof being only a few feet above the level of the ditch should not afford a bridge by which to enter the work. One of the redouts which was executed near Lisbon, being commanded by a height in its front, from whence the parapets might have been destroyed and the interior ploughed by shot, there was formed a gallery behind the countersearp, and opposite one of the angles of the work, with loop-holes, from whence the ditch along each face might have been defended by mute ketry if the enemy had penetrated into it. The soil being chalk, no timber-frames were necessary for the support of the sides or top ; and between this recess and the interior of the redout there was a gallery of communication passing under the bottom of the ditch.
A row of palisades is frequently planted quite along the ditch of a redout. Sometimes also the escarp of the work is fraized, or fur nished with palisades planted in an inclined position, and a line of elsevaux-de-frize is disposed upon the berme. In order to retard the advance of an enemy, the work is generally surrounded, at a distance not exceeding the range of musket-shot, by a single or double abatis, and often by two rows of pits called trous de loop.
The magnitude of a redout, whatever be its form, is determined by the strength of the garrison and the quantity of ordnance by which it is to be defended ; all the men being supposed to be lodged within it. It was formerly the practice to allow on the area of the terreplein, within the foot of the banquette, ten square feet for each man, and 824 square feet for each piece of artillery; consequently when the redout is of a square form, the breadth of the banquette being known (about 11 feet), the length of the erestline on each face could be easily determined. In order that the defenders may conveniently use their arms on the banquette, it has been customary to allow three feet along the crest of the parapet for each man, who is to stand con tiguously to the interior slope ; and it was once considered that a redout intended to make a considerable resistance when attacked on all sides, would be adequately garrisoned if the number of men in it were equal to the number of feet in the whole length of the crest of parapet; that is to say, if there were three ranks of men along each face, the work being supposed to be capable of containing such a number. It is said that each side of the square redouts which Marshal Saxe caused to be constructed at the siege of Maastricht, in 1748, was above 100 feet long, measured on the crest of the parapet, and that each redout was garrisoned by 500 men ; and It will be found by computation that, consistently with the above rules, a square redout, each of whose faces is sixteen yards long, is the least that ought to be constructed ; for if less, the interior within the banquette would not contain the number of men necessary to line its parapet with one rank. But the rule relating to the area within the banquette has been objected to as an unnecessary affectation of mathematical pre cision. The British engineers who constructed the works for the protection of Lisbon observe that, except at night, or at the moment of being attacked, part of the garrison will be on watch, or otherwise occupied outside of the work ; and even at those times at least one third will be under arms on the banquette. Colonel Sir John Jones states that the strengths of the garrison were finally determined by allowing two men per yard in the length of the parapet for the exterior works, and one man per yard for the interior works ; deductions being made for the spaces where artillery was to stand. Each gun takes up about eighteen feet of the length of a parapet.