When the roof of a magazine is covered with earth to the height of several feet, for the purpose of securing It effectually against the effect of falling shells, the rainwater &boort"d by the earth may st length penetrate through the brickwork to the Interior of the building. In order to prevent this effect it has been proposed that the roof should be (levered with common hollow tiles, having their concave surfaces upwards, and that, over these, boards should be laid to carry the earth. The absorbed water would thus drain off in the channels formed by the tiles, and be conveyed away by the gutters between the roofs.
Temporary magazine', such as are formed to supply the batteries in a siege, are necessarily made of wood. They are of three descriptions, the rectangular, the lean-to, and the triangular.
The leareto magazine, which was the one principally employed by the British army In the Peninsula for field powder magazineseis formed by laying stout timbers, generally termed splinter-proof timber, at an angle of 45', sloping towards the fortress, against an earthen parapet (reveted interiorly), so as to enclose a space of which the section is nearly a right-angled triangle. The splinter-proof timbera are then covered with earth; from its great inclination this face is well able to resist the effects of vertical fire or shella falling on it, while the powder is protected in front by the parapet from the effects of shells tired horirontally. This forum of magazine, however, is very ill adapted for stowage.
The triangular field powder magazine, the section of which is an isosceles right-angled triangle, is also bad for stowage, and takes long to construct. It may, however, be placed in a traverse or parapet. The size as adopted at Chatham was 15 feet 6 inches iu length of body of magazine, 6 feet 6 Inches wide at bottom, and (3 feet 6 indica high in the clear ; or, with the length inereaaed to 18 feet to allow of a low passage, 2 feet 6 inches wide and 4 feet ti inches high, leading perpen dicularly from one end of the magazine to the rear. The Interior form
of the magazine is preserved by five triangular frames of carpentry, with sheet planks and famines in front. The body of the magazine may be sunk 4 feet.
The rectangular field powder magazine, which is the one now gene rally adopted in the British service, consists of a rectangular excavation 12 feet 3 Welles long by 6 feet 3 inches wide, with a passage at right angles to its length at the end of one side, running to the roar. The sides are formed by rectangular frames 4 feet 9 inches high and 4 feet 4 inches wide from alt to out ; behind these, to support the earth, sheeting planks 1 inches thick are placed. Over the top, supported at each end by the frames, are splinter-proof timbers About 6 inches In width by 9 inches in depth, the whole being covered with earth to the thickness of about 5 feet. The sheeting is not carried along the whole of both sides, but stops short of one frame, which is the entrance from the passage, the passage being formed something like the gallery of a urine ; the frames of the prussago are only 2 feet 2 inches wide. There are then four body-frames, two on each side, opposite to one another, and four passage-frames, two in the body of the magazine, opposite to one another, and two more for the continuation of the passage to the rear. The tops of the frames are on the level of the ground, the magazine being sunk below that level; and a small ditch, which supplies earth for cover, surrounds the megazino, leaving a para pet of about 4 feet in breadth all round it. 'rids is the beat description of field magazine, especially for stowage.