MAGAZINE. Powder, a building constructed for keeping large quantities of powder. These magazines were formerly towers erected in the town-walls ; but many inconveniences attending this situation of them, they are now placed in different parts of the town. They were at first constructed with Gothic arches; but M. Vauban, finding these too weak, constructed them in a semicircular form, of the following dimensions : 60 feet long within, and 25 broad ; the founda tion S or 9 feet thick ; and S feet high from the foundation to the spring of the arch; the floor about two feet from the ground, to prevent damp; and consequently six feet for the height of the story.
The thinnest part, or haunch of the arch, is three feet thick, and the arch made of four lesser ones one over the other, the outside of the whole terminating in a slope to firm the roof ; from the highest part of the arch to the ridge is eight feet, which makes the angle somewhat greater than ninety degrees ; the two wings, or gable ends, are four fret thick, raised a little higher than the roof, as is customary in other buildings : the foundations are five feet thick, and as deep as the nature of the ground required. The piers, or long sides, are supported by four counterfoils, each six feet broad, and four feet long, and their interval twelve feet; between the intervals or the counterfeits are airdu des, in order to keep the magazine dry, and free from dampness ; the dices of these air-holes are commonly a foot and a halt' every way, and the vacant round them three inches, the insides and outsides being in the same direction. The dices serve to pre vent an enemy from throwing fire in to burn the magazine; and, for a thriller precaution, it is necessary to stop these holes with several iron plates, that have small holes in them like a skinoner, otherwise fire might lie tied to the tail of some small animal, and so drive it in that way ; this would be no hard matter to do, since, where this precaution had been neglected, eggshells have been found within, that have been carried there by weasels.
To keep the floor from dampness, beams are laid length. wise, and to prevent these beams from being soon rotten, large stones arc laid under them ; these beams are eight or nine inches square, or rather ten high and eight broad, \\ bleb is better, and eighteen inches distant from each other; their interval is filled with dry sea-coal, or chips of dry stones; over these beams are others laid crosswise, tom' inches broad and live high, which are covered with two-inch planks.
Belidor would have brick walls made under the floor, instead of beams, and a double floor laid on the cross-beams ; but the plan above described is, we think, preferable.
To give light to the magazine, a window is made in each wing, N‘hich is shut up by two shutters of two or three inches thick, one within and the other without it ; that which is on the outside is covered with an iron plate, and is fastened with bolts, as well as that on the inside. These windows are made very high, for fear of accidents, and are opened by means of a ladder, to give air to the magazine in tine dry weather.
There is likewise a double door, made of strong planks, the one opens on the outside, and the other within ; the out side one is also covered with an iron plate, and both are locked by a strong double lock ; the sto•e-keeper has the key of the outside, and the governor that of the inside : the door ought to face the south nearly, it' possible, in order to render the magazine as light as can be. and that the wind blowing in may be dry and warm. Sometimes a wall of ten feet high is built round the magazine about twelve feet distant t'roto it to prevent anything from approaching it without being seen. Mr. tiller has proposed some alterations, by way of improve meat, in M. Vauban's construction.
If large magazines are required, the piers or side walls which support the arch should be ten feet thick, seventy-two feet long, and twenty-five feet high; the middle wall, which supports the two small arches of the ground floor, eight feet high, and eighteen inches thick, and likewise the arches : the thickness of the great arch should be three feet six inches, and the counterfoils. as well as the air-holes, the same as before. Magazines of this kind should not be erected in tbrtitied towns, but in some inland part of the country near the capital, where no enemy is expected.