Galerie tranversale, Fr. is a gallery in fortification which cuts the capital in a perpendicular direction.
Galerie meurtriére ou de premiere envelope, Fr. a gallery which runs under the whole extent of the covert-way, and is frequently carried close to the counterscarp, in order to afford a circulation of air.
Galerie d’envelope, Fr. a gallery which is constructed at the extremity of the glacis, and is commonly made parallel to the magistral or principal line of fortification. The envelope is the chief gallery in a fortress or garrison-town, and serves as a path of communication or covered way to all the rest.
It is of the utmost consequence to the besieged to secure this gallery from every approach of the enemy; and if any impression should be made, to repair the injury without delay. From this gallery the garrison always direct their attacks, whenever it is necessary to keep the assailants out of the covert-way.
Galerie d’écoute, Fr. a gallery in front of the envelope. Ecouter, which signifies to listen, sufficiently explains the purpose for which these galleries are erected.
Petites Galeries, ou rameaux, Fr. small galleries, branches, or arraignées, in fortification, which issue from the counter-mine, and at the extremities of which the furnace or chamber for the lodgment of gunpowder is constructed. There is not any established or fixed rule to direct the height to which small galleries, branches, or arraignées ought to be carried; in general they should have the least possible elevation.
When galleries are built of mason-work their height is from five to six feet, their breadth from three to four, and sometimes only three.
Galeries de mines, Fr. galleries in mining differ from counter-mines, in as much as that they are supported by coffers resting upon frames, which are covered with earth three feet in depth; that is, two feet and a half from one frame to another. These galleries are usually built three feet and a half high, and two and a half broad; and whenever there is a necessity to work in the rameau or arraignée, the galleries in that case are reduced to smaller proportions.
Galerie magistrale, Fr. in mining signifies any covered avenue or gallery which is parallel to the magistral or principal line of the place, and exists under the whole or part of the front of the fortifications. This gallery is usually as thick as the enemy’s mason-work against which the counter-mine is directed. By means of this work, the besieged generally endeavour to interrupt every attempt which the besiegers may make in the passage of the fossé or ditch.
Galerie à passer un fossé, a gallery constructed for the purpose of crossing a ditch. It is a small passage made of timber-work, having its beams or supporters driven into the bottom of the ditch, and being covered at top with boards that are again covered with earth, sufficiently strong to bear the miner, and to withstand the effect of artificial fire, or the weight of stones which the enemy might direct against them. This sort of gallery is sometimes called the traverse, or cross way.