288 SERVICE OF ARTILLERY

attack should be made in this cafe ; which will induce theenemy to march with greater expedition to raise the siege.

95. Whatever be the motive for undertaking this kindof siege, the batteries ought to be amply furnished withcannon and mortars; they should be fired at different eleva-tions from 8° to 12 0 that the shot and shells may be throwninto every quarter of the town t and if there be a probabilityof setting fire to any of the principal edifices or magazines,hot-shot should be incessantly fired.

From a review of every circumstance attending the com-mencement and progress of sieges, it Will appear that fromthe opening of the trenches until the surrender of the place,the nature of the siege may, from the variety of incidentsto which military operations are peculiarly liable, be fre-quently changed.

CHAP. X.

Directions for demolishing the Fortificationsof a City.

96. Xt is generally deemed sufficient - to demolish therevetements of the works, and blow up the magazines,casemates, &c.; the destruction seldom extends to the terre-plein, from the great expence and labour it would cost.

The chambers of mines for demolishing a building, thewall of which is not more than 7 feet thick, are of a cubicalform , with one of the sides corresponding to the side of thewall; but if the thickness of the wall exceed 7 feet, cham-bers are made in a hemispherical form , in the centre of thewall.

97. The following are the general principles to be ob-served in the disposition of mines :

1. The chambers should be made at the foundation,that the upper part of the building may be raised andshaken to pieces;

2. And, if possible, some feet below the surface ofthe ground on which .the wall stands; as from thegreat resistance the explosion is more violent, and theeffect greater: mines placed near the surface of the

ground