LUNETTE, in fortifiestion, is a work similar to a ravelin, or demi• lune, but generally of smaller dimemdons. Such works have beer placed in the retired angles between the ditches of a bastion and of the collateral ravelin, but they are now usually considered as advanced works, and are placed in front of those just mentioned.
The form of a lunette is the same as that of the redoubt Y in the plan at the end of the article FORTIFICATION ; and its positions may le understood by conceiving such works to be placed beyond the glacis s on lines passing through r and a, x and n, and produced. Each lunette is protected in front by a ditch beyond which is a covered.wmmy, as usual.
The best disposition for a series of such works is that in which they are alternately more and lees odvanced beyond the fortress; since the': they afford one another a reciprocal defence by the crossing fires whicl may be kept up from the nearest faces of every salient and retiree lunette. And should the besiegers succeed in carrying their approaches rip the glacis of the latter, the artillery on the flanks of the two mor salient and collateral lunettes would effectually preveut them Iron: forming a battery on its crest to breach the work. The operation: against any one retired lunette must consequently be postponed till the two collateral lunettes arc taken ; whereas had all been equally advances: beyond the fortress, the three might have been breached and assaulteC at the same time.
To give the more advanced lunettes, which are generally those place(' beyond the ravelins;a11 the advantages of which they are susceptible the magistral lines of their faces should coincide with the sides of ar equilateral triangle whose bare is a line joining the faces of the twc collateral bastions at points about twenty or thirty yards from thei; flanked angles ; for thus the earthen parapets at the salient angles cc the lunette will not be wally destroyed by rain, and the ditches befog the faces of the work eau be defended by two or more pieces of artillery conveniently placed on the faces of the bastions. The ditches of the retired lunettes should iu like manner be defended by artillery placei on the faces of the collateral myelitis; and the magifitral hues of GAL faces should consequently be directed towards such ravehins.
In a front of fortification of the ordinary extent (360 yards) this rub for placing the advanced lunette, will permit the ditch and covered-wal of the latter to be defended by a fire of musketry from the retires places of arms t. t(Fonstricartox], and from the covered-way before
the bastions ; and, that such fire may graze the bottom of the ditch o the lunette, this ditch ought to be in an Inclined plane nearly coinciding with the slope of the glacis a a. Should the ditch so formed be to shallow to fulfil ita end, which Is that of being an obstacle to the enemy in his attempt to assault the lunette, it would be necessary ts make it deeper ; and that it might not thus become a trench in whirl the enemy would be covered from time fire of the defenders, it d10111( communicate with water, by which it might be filled previously to the expected assault.
The rampart of a lunette differs In no respect from that of othe works ; it should have the same relief, or height above the nature ground, as is given to the reedit's; since, as In the latter work, the fin of artillery should be capable of being directed against the trenches o the enemy at the foot of the glacis, over the heads of the defenders or the banquette of the covercal.way. Its escarp should be reeked witl brick or atone, in order that the enemy may be compelled to form tetsch in it by artillery, or by a mine, previously to making an assault or at leant that the attack by escalade might be a process of and danger. The terreplein, or ground in the interior, should be higl enough at the page to prevent an enemy from entering there wIthou acalingdadders ; this part should be further protected by a loophole wall, or a line of palisades; it should be seen and defended from som collateral work, and en open C31101Miere, Or a subterranean gallery, fo communication, alioulcl lead from the gorge of each lunette to the pine of arms in its rear. The advanced ouvertel.way should pass in front o all the lunettes, and it might tern inate at the two extremities on inac cessible gnautel, or in the general covered-way of the place.
Advanced burettes about a fortress form strong poets for artillery by which an enemy is compelled to commence hr. approaches at greeter distance than would otherwise be necessary. The length of their faces, may be from sixty to seventy yards, and that of their flanks from fifteen to twenty. It ma considered that a wellelisporued series of these works would prolong the defence of n place about ten or twelve clays. Rut they are only proper for fortresses of the first magnitude, since they would require n large garrison ; and the troops on being compelled to retire, might not find sufficient room in a small place.