Batteries are places for guns, being mounted on plat forms, round which a parapet and a ditch are constructed towards the enemy.
Traverses are similar to the works of the same name formerly described. They consist of mounds of earth, and are constructed to hinder certain lines from being enfilad ed, or to cover troops.
Cavaliers of the trenches are traverses 10 to 12 foet high, constructed on the saliant angle of the glacis, about 10 to 30 feet from it, in order to enfilade the covered way, and to drive its garrison out of it. There are steps behind, by which to ascend them.
The approaches and parallels are conducted according to certain rules, the capital, and its prolongation in the field, being the principal line for the construction of all the works. On a plan of the fortress these capital lines are drawn, and the first parallel laid down at about 600 to 1000 paces distant from the covered way. The approach or communication between the camp and the parallel is next determined, in such a manner, that the angles of its zig zag are as near to the capital line as possible, and that they form the shortest unenfiladed way to the parallel. The nearer the trenches come to the place, the smaller are the turns and the angles of the approaches ; but the longer time will be taken in approaching the fortress. That part of the approaches which is the most distant from the for tress, is called the tail, and, on the contrary, that which is the nearest to it, the head of the approaches.
The first and second parallel, when a fortress is not very strong, are generally like those represented in Plate CCLIX. Fig. 2 ; but if the polygon which is attacked be well forti fied, Fig. 1, is preferred. The third parallel is generally constructed at the foot of the glacis, and a fourth is some times also necessary.
The figure of the parallels, as well as the approaches, being thus laid down, the places of the batteries are next determined. There are three different kinds of batteries, viz. dismounting, ricochetting, and breaching batteries. The former serve to dismount guns, or so to damage them, or the parapet before them, that they must be withdrawn, and that the men behind' the remaining parts of the para.
pet may be exposed to the fire as much as possible. Rico
chetting batteries serve to enfilade the lines, in the prolon gation of which they are placed. This consists in firing with small charges at a particular elevation, by which the shots roll along the inside of the parapet. Breaching batteries serve to make breaches in a work, or to destroy a part of its revetement, rampart, or other inclosure, in such a man ner that it may be attacked and mounted with little or no difficulty.
The ricochetting batteries are generally placed at the first or second parallel, in such a manner that they may en filade the faces and flanks of all the works on the front which are attacked, and even some of the next, as also the covered way, and the works situated before it. They are therefore constructed in their prolongation of these lines. The dismounting batteries are generally constructed at the second and third parallels, or between both ; and are paral lel to such works as they are intended to annoy.
The breaching batteries are sometimes at the last pa rallel ; but they are still more advantageous NA hen on the crest of the covered way.
The guard placed for the defence of the trenches should never be less than the garrison (.4 the place. It always re mains 24 hours in the trenches, and is generally relieved towards the morning. If possible, this guard is always composed of whole battalions,bttt never of too large a force front one part of the camp, lest that part should be too much weakened. The sentries in the trenches arc to be as nu merous as possible ; and they always give notice of every shot of the garrison, that every one may secure himself. Cavalry arc ordered to cover the ends of the trenches, and to make an attack on the enemy's flank, if he comes out of the fortress. The whole guard of the trenches is com manded by a general ; but besides this, the major of the trenches has the immediate superintendence of them, and of the police there. He shews each battalion its place, and gives every commander his proper instructions. He gene rally has two to four assistants, and is always accompanied by some orderlies, to execute his orders. It is his busi ness, also, to attend the market, to order the provisions, and to see that a proper degree of cleanliness is observed in the trenches.