Engineering Wonders of the World
Volume I

402 ENGINEERING WONDERS OF THE WORLD. plate, is made of lesser diameter. The bolt, if weakened, would stretch or break at this weakest part rather than at the thread. Fin- ally, the nut securing the inner end of the bolt to the ship is fitted with a rubber washer in order to absorb shock. Above the main belt is usually placed a second armour-strake of thinner plates. Sim- ilarly, the thickness of the armour forward and aft of the main gun positions is not as a rule nearly so great as at the centre. The armour in the bows is carried higher than in LIFTING AN ARMOUR-PLATE INTO POSITION. (Photo, S. Cribb.) The great thickness of the plate may be gauged by the comparative size of the hands of the man in the foreground. the stern, as a protection against damage there that might lessen a ship’s speed by the admis- sion of water. Supporting the belt, and next to it in im- portance for the defence of the hull of the ship, are the armoured decks. There are usu- ally two of these, curved to- wards their centre section, and carried down on either side to and bottom of the main belt. The curve is provided for two reasons—first, that a shell penetrating the side of the ship may- be prevented from continuing its passage into the vitals—that is, engines and magazines ; secondly, that sufficient “ head-space ” may Armoured Decks. meet the be given to the engines and machinery in the centre line of the ship, whilst at the sides the deck is carried well below the water-line, to prevent the possibility of projectiles entering below its edges. Armoured bulkheads divide a vessel into transverse sections, and, in the case of our latest ships of the Dreadnought type, the main bulkheads extend from keel to main-deck without a door. This is the finest insurance of the floatability of a ship that can be provided. The Dreadnought and her sisters have lifts provided to enable the crew to go up and down be- tween the various decks. In addition to the bulkheads, we have many other protective items of a ship’s construction, amongst them cofferdams— half-bulkheads into which can- vas, oakum, or other material can be jammed during an action to limit the flow of water across the deck should one of two compartments so divided be pierced. Then there are armoured scuttles and gratings, and slanting plates around the uptakes of the funnels between decks to prevent damage here, and the subsequent filling of a deck with smoke and gases from the furnaces. With every improvement in armour there has been an almost immediate improvement in the shell to attack it. As far back as 1894 Messrs. Thomas Firth and Sons of Sheffield suggested “ capped shells ”—that is, a shell fitted with a cap of comparatively soft metal which on impact would break up, star the plate at- tacked, and allow the shell proper to apply its whole force in piercing the plate. This firm, in December 1907, gave a new 12-inch common shell a trial against a 9 j-inch Krupp cemented plate, fitting the projectile with a cap. It