Permanent Powder Magazines.—According to Vauban’s plan, powder magazines are commonly made 10 fathoms long, and 25 feet wide, in the clear. The foundation of the longest sides, is 9 or 10 feet thick, and 6 feet or more deep, according to the nature of the ground. The side walls raised upon these are 8 or nine feet thick; and if there is not to be an upper story, 8 feet will be sufficient height above the foundation. By this means the flooring maybe raised above the ground, free from damp, and there will remain 6 feet from the floor to the spring of the arch. The arch is formed of layers of bricks, arched one over the other, and ought to be 3 feet thick at the top. The exterior surface of the arch terminates with, an angle at top, like a roof; which angle must be of such magnitude as to make a thickness of 8 feet over the key stone of the arch. The foundation at the gable ends is 5 feet thick, and the same depth as the sides; these ends are built up 4 feet thick, from the foundation to the top of the roof. The long sides are supported by counterforts, 6 feet thick and 4 feet long; and placed 12 feet asunder. The ventilators are placed, one in the centre of each space between the counterforts, and are made with a die across them of 1½ feet. These ventilators are also closed with plates of iron. The magazine is lighted by a window in each end, high up, which are opened and shut by means of a ladder. These windows are secured, each by two shutters, made of plank 2 or 3 inches thick; and the outer one covered with sheet iron, and both fastened with strong bolts. The entrance to the is closed by two doors, one of which opens inwards, and the other outwards; the outward one is covered with sheet iron. The entrance of the magazine should, if possible, be placed towards the south. A wall of 1½ feet thick, and 10 feet high, is built round the magazine, at 12 feet distance. A magazine of the above dimensions will contain about 94,800 lbs. of powder, in piles of 3 barrels each; for a greater number piled above each other destroys the barrels, damages the powder, and occasions accidents.
MATCH.—The slow match used by the English is made by contract: one yard of it will burn about 8 hours. The French slow match is usually made by soaking light twisted white rope for three days in a strong lye. It burns about 3 feet in 6 hours.
Slow match was made at Gibraltar, during the last siege, in the following manner: eight ounces of saltpetre were put into a gallon of water, and just made to boil over a slow fire; strong blue paper was then wetted with the liquor, and hung to dry. When dry, each sheet was rolled up tight, and the outward edge pasted down, to prevent its opening; half a sheet, thus prepared, will burn 3 hours.
Quick Match.
| Compositions. | ||
| Worsted Match. | ||
| Worsted | 10 | oz. |
| Mealed powder | 10 | lbs. |
| Spirits of wine | 3 | pints. |
| Water | 3 | ” |
| Isinglass | ½ | pint. |
| Cotton Match. | ||
| Cotton | 1 lb 12 | oz. |
| Saltpetre | 1 8 | |
| Mealed powder | 10 | — |
| Spirits of wine | 2 | quarts. |
| Water | 3 | pints. |
The worsted or cotton must be laid evenly in an earthen or other pan, and the different ingredients poured over it, and about half the powder: being left a short time to soak, it is afterwards wound smoothly on a reel, and laid to dry, remaining half of the powder is then sifted over it; and it is ready for use when dry.
Note. The French have lately made their slow match by soaking the rope in a solution of sugar of lead and rain water: in the proportion of ¾ of an ounce of sugar of lead to one pint of water; and this, they esteem as preferable to the old sort.
MARCHING.—The Quick step, 108 paces per minute, each of 30 inches; making 270 feet per minute.
Wheeling Step, 120 per minute, of 30 inches each; making 300 feet per minute.
Side Step.—12 inches—75 per minute.