The second parallel is constructed exactly in the same manner as the first ; but the work being much more dan gerous, from its being nearer the fortress, it ought to be executed with the greatest possible secrecy and dispatch. If any part of the parallel has been left unfinished during the night, it should be done the following clay, or, at far thest, in the course of next night. After this, the approaches towards the fortress are continued in the same manner as before.
If any point peculiarly favourable to the construction of ricoehett batteries should occur, advantage is to be taken of it, even in preference to those which it had been previ ously proposed to raise. All sallies made by the garrison are to be met by the guard of the trenches, while the ca valry is endeavouring- to cut olf the enemy's retreat. The guns on the batteries should always have grape-shot ready, and as soon as an attack of the enemy is perceived, should be fired at those parts against which the attack is directed.
In order the better to observe the motions of the enemy, the ground before the parallel 5 should be illuminated either by fires, or by light-balls. The third parallel is the next part to be constructed ; or iF it lies too near the enemy, the dismounting batteries are first to be constructed. The proper situation for these is either before or on one side of the approaches, or before the third parallel, executed in a similar manner as the ricochetting batteries, only that they must be parallel to the faces and flanks. The firing from these batteries, as formerly observed with regard to the others, is not to commence till they are completely ready in every respect ; but when once opened, a constant firing is to be kept up, and the guns should be fired at the same time, in order to cause as much confusion as possible in the place.
As the construction of works between the second paral lel and the place is very dangerous, an ingenious method has been devised for covering the workmen by means of the sappe. This consists in placing gabions or baskets in the line where a of the trenches is to be constructed, and filling these baskets with earth, so that they serve to hide the men, and to cover them from the fire of small arms.
There arc three different modes of conducting the sappe, viz. the flying sappe, where all the baskets arc placed at once by a number of men, and then filled as soon as possi ble ; the half sappe, where all the baskets are placed at once, but filled successively ; and the complete sappe, where the baskets are placed successively, so that the man who places one is covered by the preceding one, or by a large bag, or a basket full of earth rolled before him. In
stead of the basket, or sack full of earth rolled before the men, a blind or board resting on two small wheels, with a thili, is made use of.
The flying sappe may be made by common workmen, and also the half sappe ; but, in constructing the complete sappe, men called sappers must be employed, who are par ticularly acquainted with this business. Of these men,,a sappe will require at least four. The first places the bas kets, and partly fills them with earth, while he digs a ditch behind them two feet deep, and two wide. Ile also places small bundles of rods, fascines, or sand-bags, between every two baskets. The three that follow him enlarge the fosse half a foot in depth, and as much in width. These four men take each others places successively, and arc relieved every two to four hours by new ones. This work can be conducted by night as well as in the day-time ; but not more than from 20 to 30 yards can be completed in one day.
There are also three different kinds of sappes, distin guished by their figure, viz, the simple, the double, and the covered sappe. The first has baskets filled with earth, or a parapet, only on one side ; the second has a parapet on both sides ; and the third has not only a parapet on both sides, but also a shell-proof covering.
The construction of the simple sappe has been already explained. The double sappe is constructed by making two simple ones alongside each other ; and the covered sappe is made like the double, but as soon as possible co vered with rafters, and overlaid with earth. The covered sappe is generally deeper than the simple or double one. The direction of the sappe is also different, being either zigzag, as A, Plate CCLIX, Fig. 3 ; right-angled, as B ; in the snake-form, as C ; or with traverses, as D and E. That which is in form of a zigzag, is used in approaching the third parallel ; that with right angles, on the covered way ; the snake-form, in tunnels of mines; and that with traverses, in approaching the covered way, or where cir cumstances require a safe and good communication, which at the same time may in part be used as a place of arms.