As soon as the first parallel has been finished, the rico chett batteries are constructed. These are placed either in, before, or behind the parallel, according to circum stances.
The space between every two guns is generally 24 feet ; and between the mortars, about 15. The depth of the bat teries is from 30 to 36 feet ; and a powder-magazine is ge nerally placed behind them. The guns on such a battery are mostly placed at the ends, and the mortars in the mid dle. Besides the ricochett batteries, others are constructed to fire at the magazines of the fortress, in order, if possi ble, to destroy them. Such batteries also may be advanta geously constructed, even before the trenches are opened, on heights commanding the town ; and mortar-shells filled with combustible matter, or red hot balls, as well as fire rockets, may here be of great use, in obliging a fortress to surrender long before a breach has been made. A battery in the parallel, however, is constructed in the shortest time, and therefore often the best. Its construction is as follows : The parallel is made. equal in width to the depth of the battery ; the platforms for the guns are laid ; the inside of the parapet is finished to the height of the soles of the em brasures, and the embrasure begun ; then the parapet is finished ; and afterwards also the embrasures, which gene rally, as well as the interior talus of the parapet, are lined with fascines. The batteries for mortars have no embra sures, but are lined like those for guns. The parallel is in this case conducted round the battery, viz. behind it, in the same manner as PARALLELS are built. The battery has generally a parapet, either at its flanks, or before them, but none behind.
A battery before or behind the parallel is dug out, in quite a different way. The inner talus is determined at first at a proper distance front the parallel, and fascines be ing laid down to mark it out, a ditch is dug out before it, and the parapet constructed in the same manner as direct ed in field-fortifications, observing the above rules with re gard to the construction of the embrasures. The two wings or flanks of such a parapet are joined to the paral lel, and serve to secure the communicalkin with it. At the back of these batteries, generally behind a small tra verse, a powder-magazine is constructed to contain am munition enough for two days, or about 200 shots for each gun, and 150 for each mortar.
The men employed to construct such a battery, should be acquainted with the work. These batteries being also constructed during the night, will hardly be complete the next morning ; and therefore they are sometimes construct ed only of fascines, or, what is still more expeditious, of sand-bags, if they can be had.
It will be also an advantage, if these batteries can be re.. gularly traced, and constructed by such a number of men as do not impede each other in working, but who may al ways be fully employed during the time they arc there. If these labourers can -be relieved every two hours, this will forward the work very much, and considerably lessen the time usually required.
As soon as the ricoehett batteries are finished, and also the first parallel, the fire of these batteries is to begin. Not a gun, however, is to be fired from any of them till they arc completely finished, lest they should attract the enemy's fire ; as this would molest the workmen, and only give rise to confusion, which might occasion the total destruction of a battery, or the dismounting of its ordnance. When the fire from a battery has once begun, it is to be kept up dur ing the day-time ; and if the guns can be levelled at night, the fire should never cease, that the enemy may not be al lowed to repair any parts which have been damaged during the clay. The fire is to be made at certain intervals, and never two shots at the same time from one battery, that the enemy may always be in a state of alarm. The artillery men on one battery are divided into certain parties, one of which always serves the guns. An officer has the inspec tion of each battery, to observe its effect, to correct its le velling, and to make such repairs as may be readily done at the moment, but which, if neglected, might lead to more serious consequences. Every officer, therefore, is to be made answerable for the effect, and the accidents in his battery. ' After finishing the parallels and the batteries, those places on the parallel are to be determined from which the approaches shall commence. An opening is then cut in the parapet of the parallel where the workmen are placed to cut out the approaches, covered in a similar manner as in the first night. The soldiers serving to guard these workmen are, if necessary, covered by woolsacks, which they carry with them, and which, being about the height of three feet, will cover a man completely.