=88. The Attack.=--The besieger should advance by several galleries, securing those on the flank by listeners. He must be active and persistent, as the enemy will use every available moment to develop his countermines. When he receives the first camouflet of the defence he must hasten to fire his overcharged mines in the uninjured branches, in order to destroy the hostile countermines. He will generally suffer losses more or less heavy from this epoch forward, but must submit to them; since too much circumspection and delay will almost always result in complete failure. Before firing the overcharged mines he must have everything in readiness to occupy and intrench himself in the craters formed; to open communication from the trenches to the craters either by sap or by forming a line of connecting craters; and for constructing shelters for the party occupying the craters and holding them against the sorties of the defence. After occupying the craters, he should drive forward his galleries from them at once, unless the besieged has anticipated him and surrounded the craters with branches--which may be assumed to be the case if any delay has occurred in occupying it. In this case he should sink shafts à la Boule, heavily overcharged, and fire them, and immediately occupy the new crater and push out from it; and thus progress as rapidly as possible, by constantly placing and firing overcharged mines, whose craters will, with little alteration, form both communications and parallels. When the fire of the defence upon the crater is so severe that a deep shaft cannot well be sunk, a shallower one with correspondingly small charge is first sunk and fired, and a deeper one is sunk from the crater thus formed. The overcharged mines should be well tamped when time permits. If not well tamped the charge should be increased (_or high explosives used._--J. M.). =89. The Defence.=--The defence should push out his galleries as far as possible and at the earliest practicable date, connecting them by transversals for ventilation, and holding them at a level below any likely to be reached by the attack. When near the enemy, he should stop work several times a day and listen for sounds from the hostile miners which will locate their position. Hearing the sound of the enemy’s miner, he may work toward him noiselessly, or prepare and charge a chamber and await the approach of the miner toward it, listening at the point where the hose trough (_tube for fuse wires._--J. M.) comes through the tamping until the enemy is near enough to justify firing. Judgment as to distances must be formed from practice obtained while driving the countermines. To avoid forming craters on the surface, and to do the greatest possible damage to the besieger’s works, the besieged should not fire his mine until the enemy’s distance from it is less than the line of least resistance reckoned toward the surface.