pets, should be regularly mown fur the same purpose.
The counterguard B is solid, as is also the rampart A; its terre-pleine H is considerably lower than that of A, which commands it, both by the cannon it mounts, and by its musquetry ; the parapet being sloped so as to give a di rect fire into it, when the firelocks are hid upon the slope at x. In this couo terguard the interior of the parapet is not reveted; therefore the banquette 1, as cended from the terre-pleine, H, by a slope of gazon. The parapet C, &c. are nearly the same dimensions as F on the rampart A, except that the rampart B is much lower than A. The exterior of B has a cordon, level with the terre pleine H, but its parapet is faced with turf, which the cordon assists to sup port. if the counterguard B were not defended by other out-works in its front, it would have a glacis come close to it, leaving only a very small passage be tween its exterior and the palisades ; here we suppose it to have a small dry ditch D, reveted both in the scarp and counterscarp, but without a berm, which is very rarely, if ever, allowed to an out work.
The third figure affords a more gene ral profile of the works, and gives some idea of the usual defilement of the out works, B and C, from the body of the place A. D is the foot of the glacis, where it meets the terre-pleine, or level of the country,'which we always sup pose to be esplanaded, (that is, laid flat) and not affording any cover to the ene my for at least 100J yards from the out works. The glacis is usually made full 50 yards long, and of such an ascent as to give, on an average, about eight feet Neigh at its crest. Supposing the angle of the raveline to be 25 yards within the crest of the glacis, the continuation of the ascent would strike the cordon of the rampart, C, at 12 feet from the level of the terre-pleine ; this determines the height at which a cannon, standing on the terre-pleine of the raveline, C, would graze the glacis, while the slope of the embrazures would allow the guns to play into the covert way. It is ob Nerved, that, according to this construo qion, all the scarp, below the cordon, is completely hid from the enemy, and can not be battered, so long as the crest of the glacis remains at its proper height.
ence partly arises the great difficul y of breaching the saliant angles of out orks.
Now let us estimate the redoubt, B, at 25 yards within the flanked angle of the bastion C. It is to be remarked, that this defence is made with the view to render the raveline untenable to an enemy ; and that, for the preservation of its parapet, the rampart of the re doubt, B, should be a mere trifle above the level of that of the raveline, C. The faces of the contiguous bastions of the same front enfilade the faces of the raveline ; but it is always requisite, that the fire from the curtain should, on emer gency, (for the bastions may be silenced) contribute to drive the assailants from that part of the raveline which lays be yond the redoubt ; at all events to clear its ramparts. Therefore we will state the terre-pleine of B at only one foot above that of C. This puts the redoubt com pletely out of the hoe of defilement, and, in fact, generates another, by allowing the curtain, A, to throw shot into C, with out touching any part of B, as may be seen by following the line from the cor don of A to the terre-pleine of C. Hence B cannot be battered from the glacis.
But where it is necessary to produce the greatest accumulation of strength against any exterior point, it is often found proper to raise every part of the interior defences, so that they should all overlook, like a flight of steps, as shewn in fig. 4, where the citadel is supposed to stand on a conical hill, high above the town, (which is only defended by a glacis and covert way, surrounding a ditch and rampart) and has four rows of cannon, at different heights, each com manding the exterior defences, and the surrounding country, as far as the shot can reach. This, though not a com mon figure, nor a common mode of for tifying such places, (for works are rare ly carried like hoops or bands around hills) will fully illustrate the general ten dency of the foregoing details, and to the ordinary reader, who cannot here expect to find all the minute items and varieties abounding in this very intricate science, will give a tolerable insight into the prin ciples on which fortifications are usually constructed.