While she was being built a new type of cannon was perfected which gave greater power with less weight and she was armed with these improved guns, each of which was of seven-inch bore and weighed between six and seven tons. Then came the American Civil War and a still newer type of armoured ship was invented. This was the ship with a turret, and the first of these was the _Monitor_. She was designed by Captain Ericsson, the same man who perfected the screw propeller, and the turret, the most important feature of this ship, is the original one from which the highly perfected turrets of to-day have developed. The idea of mounting guns in turrets had been suggested before, as a result of the experience gained in the Crimean War, but Ericsson, when he designed the _Monitor_, was the first to put the idea into practice. [Illustration: A MODERN SUPER-DREADNAUGHT _Which carries the heaviest type of guns, and is protected by heavy armour. Its speed is less than that of cruisers._] The _Monitor_ was a strange-appearing ship. The fact that she was said by the Confederates to be a “cheese box on a raft” gives some idea of her appearance. She was 170 feet long, 41½ feet wide, and displaced about 1,200 tons, but her appearance was unique. Her deck was but two feet above the water and from bow to stern she was as smooth as a paved street except for a tiny pilot house near the bow and a huge round “cheese box” amidships. This cheese box was the turret and in it were mounted two 11-inch Dahlgren guns, the _Monitor’s_ only battery. The turret was about twenty-two feet in diameter and the sides of it were of iron eight inches thick. This was built up of eight thicknesses of one-inch plates bolted together. The broad smooth deck was covered with three inches of iron and the low sides with five inches. This strange vessel was completed just in time to be sent to Hampton Roads in order to protect the wooden ships of the Union Navy from the ferocious and effective onslaughts of the _Merrimac_, a Confederate ironclad that had just sunk the _Cumberland_ and set fire to the _Congress_. This ship had been the wooden frigate _Merrimac_ which had been partly burned when the Union forces had abandoned the Norfolk Navy Yard. The Confederates had raised her, repaired her, cut her sides down almost to the water line, and had built a huge deck house amidships. This deck house, in which the cannon were mounted, had sloping walls which were covered with railroad rails. Harking back to the time of Greece, they affixed a huge ram to her bow, and then sent her forth against the Union ships in Hampton Roads. Their shells ricochetted from her armoured sides like hail from a tin roof. All the cannon the helpless _Cumberland_ could bring to bear disturbed her not at all, and slowly bearing down upon her wooden adversary she buried her ram in the _Cumberland’s_ hull. Slowly the old sailing ship filled and sank, her