1, being completed, the engineers select points near its extremities, at which they erect breast works, B.B, to cover bodies of cavalry, who are kept at hand to resist sorties from the garrison. The length of the parallel is usually made sufficient to embrace all the works of two bastions at least. Sites are then chosen for batteries, 0.C, which are built up of fascines, gabions, sandbags, and earth. They are placed at points in the parallel farmed by the prolongation of the several faces of the bastions. myelitis, and other works of the fortress, which faces the batteries are severally intended to enfilade by a ricochet fire. Other batteries will be formed for a vertical fire of mortars and shell-guns. By these means it is hoped that the traverses on the hostile ramparts will be destroyed, the guns dismounted, and the defenders dispersed. before the final approaches bring the assailants to the covered way. The sappers will now commence their advance toward the points, or salient angles, of the two bastions to be attacked. If, however, the trench were cut straight toward the fortress,'its guns could easily destroy the workmen and enfilade the approach. To prevent this, it is cut in short zigzags—as at D—the direction always being to a point a few yards beyond the outmost flanking works of the garrison. The side of each trench nearest die fortress is protected by gabions and sandbags, as in the case of the parallel. At intervals, short spurs of trench, incipient parallels, are cut, as at E, to contain small-arms-men, to act as guards to the sappers. The second parallel is about 800 yards front the enemy's works and has to he more strongly formed than the first. It often terminates in a reboubt, F, to hold some light artillery and a strong force of infantry, who could assail any sortie in flank; or it may run into the first parallel, as G, giving easier access for troops than through the zigzags. The second parallel is revet.ted with sandbags, in which loopholes are left for musketry. After firming the second parallel, the angleS of the zigzags become more acute, to, revent enfilading. At about 150 yards, certain demi-parallels,
“, are cut, and armed with howitzer batteries, to clear the coveted-way, while. riflemen also act from it. The third parallel is at the foot of the glacis. Thence the place, after being sufficiently battered, is taken by a storming-party, who make their way over the glacis, or the covered-way is topped by the double sap, which is a safer plan for the army generally, though much more deadly to the sappers When the crest of the covered-way has thus been reached, batteries of heavy artillery will be there established, for the purpose of breaching the walls of the raven!) and bastion; while at the same time minas will first seek to destroy the defenders' counter-mines (which would other wise be likely to send these batteries into the air), and then will excavate a tunnel to the ditch, at the foot of the countersearp. If the branch becomes practicable, a storming party will emerge from this tunnel or gallery, and seek to carry the opposite work by hard fighting. If inner works still subsist, which would tear assailants to pieces, the double sap may he continued across the ditch, if a dry ditch, right up the breach, that counter-batteries may be formed. If the ditch be wet, means must be adopted for a causeway or a bridge. By these means, however obstinate may be the defense, if the besieging force be sufficiently strong, and aid do not arrive from without, the ultimate success of the attack becomes certain. Vauban raised attack to a superiority above defense, first, by the introduction of ricochet fire, which sweeps a whole line; and secondly, by originating parallels. Before his time the whole attack was conducted by zigzag approaches; in which the troops actually in front could he hut few, and were therefore unable to withstand strong sorties of the garrison, who, in consequence, frequently broke out and destroyed the works of the besiegers, rendering a siege an operation of a most uncertain character.