In the disposition of the workshop, the tables, utensils, &c. are arranged, according as the judgment may dictate for convenience and use. Care must be taken to prevent the access of fire, and to prevent, as far as possible, the presence of moisture. Lanterns, if light is required, are always to be preferred; but the best manner of communicating light is through a window, placing the lights outside of the building, or apartment, as is done in powder mills. Other precautions may be necessary, which will readily suggest themselves. In conducting the work, the workmen are to be so arranged, as that, while some are employed in the preliminary operations, others are making and finishing the preparations. The compositions may be ready prepared, and well preserved in jars or other vessels. This is named by the French, _Cabinet de composition_. It is a place, also, where the substances are weighed, and mixed. _Sec. II. Of the Magazine._ The magazine is a place of deposite for gunpowder, to preserve it from fire, and moisture. We have already mentioned the preservation of gunpowder in the article on that subject; but it may not be improper to offer some remarks, respecting the construction of magazines. Authors differ in opinion, both in regard to their situation and construction; but they all agree, that they ought to be arched, and bomb-proof. The first powder magazines were made with gothic arches: Vauban constructed them in a semicircular form, to make them stronger. Their dimensions were, sixty feet long, within, and twenty-five broad. The foundations were eight or nine feet thick, and eight feet high, to the spring of the arch. The floors were two feet from the ground, for the purpose of keeping the magazine free from dampness. It is observed, that the centres of semicircular arches will settle at the crown, and their sinking must break the cement. A remedy was applied for this inconvenience, by the _arch of equilibration_, as described in Hutton's work on bridges. As, in powder magazines, the ill effect of the breaking of the cement is particularly felt, Mr. Hutton proposed to find an arch of equilibration for them in particular, and to construct it, when the span is twenty feet, the pitch or height, ten, (which are the same dimensions as the semicircle), the inclined exterior walls at top, forming an angle of 113 degrees, and the height of their angular point, above the top of the arch, equal to seven feet. A wall built round a magazine, gives it an additional security. The roof should be slated, or covered with lead or copper, and it ought to be furnished with a lightning rod, placed ten or fifteen yards from the building. The points of the rods may be either gilt, or of solid gold. Silver, however, is generally used; but, above all, platinum is to be preferred. The advantage of these points is, that they do not rust like iron, or become oxidized, an occurrence which would diminish their powers as conductors of the electric fluid.