Probably you know that each pair of big guns is mounted on a revolving platform within what is called a turret--that is, a chamber of thick armour-plate which revolves with the guns. Beneath this turret is a working chamber, some nine or ten feet in height, and from it a thick steel tube descends through the decks to the magazines below. Inside this tube, which revolves with the gun platform, are "lifts," which hoist the shells up to the barbette. The crews enter the barbettes by means of massive steel doors, which are firmly closed behind them. When the doors are closed, it is impossible for them to know what is going on in other parts of the ship, except for the little that they can observe through the sighting-hood of the guns. The steel chamber in which they are stationed is lighted by electricity, and the guns, the platform, and the hoists are worked by water power. The crew set the machinery working, and bring up a supply of shells, one of which is placed in the yawning breech of each great gun. Presently a telephone bell rings, and a voice is heard asking "if it takes a week for the barbette to get ready for action." It is the gunnery lieutenant, who is talking "sarcastic." He is in what is called the "fire-control station," which is a steel chamber high on the top of a tripod mast. In this chamber are the range-finders and all the other apparatus necessary for directing the fire of every big gun on the ship. Around the steel walls are telephones, speaking-tubes, and electric buttons. By means of very wonderful devices the officer in the "fire-control station" ranges and sights every gun in the ship. The men in the turrets have merely to obey his instructions, and fire the guns when he gives the word. "Prepare to open fire at twenty thousand yards," snaps the voice at the telephone. The machinery clangs, and the guns raise their noses high in the air. "Revolve to ten degrees on your port bow," comes the next order; and, as though by magic, the whole turret swings itself round to the required position. Then comes a pause, which the men declare is more trying to the nerves than anything that happens during the actual fighting. Little or nothing can be seen from the barbette; from the "fire-control station" the target is a mere speck on the horizon about eleven miles away. Presently the telephone rings again. "Let go with No. 1 gun" is the welcome order. The men cheer and fling themselves face down on the floor, and push home the cotton wool with which they have previously plugged their ears, to prevent the risk of deafness. The captain of the gun pulls a lanyard; there is a "kick" that makes the barbette reel, then a deafening report, as a shell weighing nearly a thousand pounds speeds over the waters on its deadly mission.