194. Ships with two magazines—one forward and the other aft—are to have them as nearly equal, in point of capacity, as the shape of the vessel and other circumstances will admit.
Magazines should be constructed as low down as possible. Their floors may rest on the keelson, but should not come below it. Their height should be equal, only, to an exact number of times the height of a powder-tank when lying on its side, in addition to the thickness of the shelving. An additional inch for each shelf should be allowed for play or spring. The whole height in the clear should be limited by the condition that a man standing on the floor may reach the upper tier of tanks with ease. Four tiers of 200-lb. tanks, three of them resting on shelves two inches thick, and the other on inch battens on the magazine-floor, will, with an allowance of one and a half inch for play and spring, require a height, in the clear, of six feet two inches. Both safety and convenience would suggest this as the maximum limit in height, even for the largest magazine. Three tiers of these tanks will require a height, in the clear, of about four feet eight inches.
If, however, in ships of great draught of water, it should be found practicable to extend the height of a magazine so as to accommodate five tiers of tanks, then the lower or ground tier may be laid so as to occupy the whole of the magazine-floor; and on the top of this tier, in the alley-way, a light false bottom is to be placed for the men to stand upon to enable them to reach the upper tier, which is the one that should first be exhausted. This false bottom should be made of gratings, and in sections convenient for speedy removal.
195. When it is impossible to avoid extending the sides of the magazine so far out towards the skin of the ship as to leave only an air-passage on either side, the crown should be at least six feet below the deep load-line.
In all cases where this crown is less than six feet below that line, the sides should be made susceptible of protection by allowing a space to interpose materials, such as sand, coal, or water in tanks, between them and the inner planking of the ship.
An average space of six feet or more on both sides will be sufficient. Under no circumstances, however well the sides be guarded, should the crown of the magazine, if it can be avoided, be less than four feet below the deep load-line.
196. It is proper to add, in connection with this most important subject, that in order to increase security against the effects of lightning, a magazine should be placed, if practicable, so as not to include a part of a mast.
197. All the metallic fixtures about a magazine, delivering-passages, and light-rooms, must be of copper.
198. Each delivering-passage is to have, for the distribution of powder, at least as many passing-scuttles communicating with the orlop or berth deck as there are chains of scuttles above. The powder-man will thus always find at the scuttle the proper passing-box.
MAGAZINE-COCKS.