MAGAZINE

, a place in which stores are kept, of arms, ammunition, provisions, &c.

Artillery Magazine, or the Magazine to a field battery, is made about 25 or 30 yards behind the battery, towards the parallels, and at least 3 feet under ground, to receive the powder, loaded shells, port-fires, &c.— Its roof and sides should be well secured with boards, to prevent the earth from falling in: it has a door, and a double trench or passage sunk from the magazine to the battery, the one to enter, and the other to go out at, to prevent confusion. Sometimes traverses are made in the passages, to prevent ricochet shot from entering the magazine.

Powder-Magazine, is the place where powder is kept in large quantities. Authors differ very much with regard to the situation and construction of these magazines; but all agree, that they ought to be arched and bomb proof. In fortifications, they were formerly placed in the rampart; but of late they have been built in different parts of the town. The first powder-magazines were made with Gothic arches: but M. Vauban finding these too weak, constructed them of a semicircular form, the dimensions being 60 feet long within, and 25 feet broad; the foundations are 8 or 9 feet thick, and 8 feet high from the foundation to the spring of the arch; also the floor 2 feet from the ground, to keep it from dampness.

It is a constant observation, that aster the centering of semicircular arches is struck, they settle at the crown, and rise up at the hances, even with a straight horizontal extrados; and still much more so in powdermagazines, where the outside at top is formed, like the roof of a house, by inclined planes joining in an angle over the top of the arch, to give a proper descent to the rain; which effects are exactly what might be expected from the true theory of arches. Now, this shrinking of the arches, as it must be attended with very bad consequences, by breaking the texture of the cement after it has in some degree been dried, and also by opening the joints of the vousoirs at one end, so a remedy is provided for this inconvenience, with regard to bridges, by the arch of equilibration, in my book on the Principles of Bridges: but as the ill consequences of it are much greater in powder-magazines, in question 96 of my Mathematical Miscellany, I proposed to find an arch of equilibration for them also; which question was there resolved both by Mr. Wildbore and myself, both upon general principles, and which I illustrated by an application to a particular case, which is there constructed, and accompanied with a table of numbers for that purpose. Thus, if ALKMB represent a vertical transverse section of the arch, the roof forming an angle LKM of 112° 37′, also PC an ordmate parallel to the horizon taken in any part, and IC perpendicular to the same; then for properly constructing the curve so as to be the strongest, or an arch of equilibration in all its parts, the corresponding values of PC and CI will be as in the following table, where those numbers may denote any lengths whatever, either inches, or feet, or half-yards.

, or Powder-Room, on ship-board, is a close room or store-house, built in the fore or after part of the hold, in which to preserve the gunpowder for the use of the ship. This apartment is strongly secured against fire, and no person is allowed to enter it with a lamp or candle. it is therefore lighted, as occasion requires, by means of the candles or lamps in the lightroom contiguous to it.

MAGELLANIC-Clouds, whitish appearances like clouds, seen in the heavens towards the south pole, and having the same apparent motion as the stars. They are three in number, two of them near each other.— The largest lies far from the south pole; but the other two are not many degrees more remote from it than the nearest conspicuous star, that is, about 11 degrees.| Mr. Boyle conjectures that if these clouds were seen through a good telescope, they would appear to be multitudes of small stars, like the milky way.