Mines, Military

Constitute one of the most important departments in military engineering, and a very formidable acce ory both in the attack and defense of fortre es. A military mine consists of a gallery of greater or le length, run from some point of safety under an opposing work, or under an area over which an attacking force must pa , and terminating in a chamber, which, being stored with gunpowder, can be exploded at the critical moment. Mines are of use to the besiegers in the overthrow of ramparts and formation of a breach; the countermines of the besieged in undermining the glacis over which the a aulting column must charge, and blowing them into the air, or in destroying batteries erected for breaching, are equally serviceable. But far above the actual mischief wrought by the mine—often very great—is its moral influence on the troops, and especially on the a ailants. Mines are either vertical,—when they are called shafts ,—horizontal, or inclined, in either of which cases they are “ galleries ,” the word “ascending” or “descending” being added, if there be inclination. The dimensions range from the “great gallery,” 6 feet 6 inches by 7 feet, to the “small branch,”—the last diminutive of the gallery,—which has but 2 feet 6 inches height, with a breadth of 2 feet. The most frequent work is the “common gallery,” 4 feet 6 inches by 3 feet, which is considered the easiest for the miner.