The most powerful weapon used in our Navy is the 15-inch gun, with which the latest of our battleships, the _Queen Elizabeth_ (launched 1915), is armed. This gun, which weighs ninety tons, throws a shot weighing five-sixths of a ton at a velocity of more than a mile a second for a range of 10,000 yards, or roughly six miles. Of course the full range of the gun is much more than this. It can make good practice at 20,000 yards, or roughly 11 miles; at six miles the gun can be laid so as to hit the target practically every time. The 13.5-inch gun, with which the battle cruisers are mainly armed, is only a little less powerful than the 15-inch gun. It throws a projectile of 1,400 lbs. weight, and can be discharged twice a minute. You will see in what ways a modern super-Dreadnought battleship differs from a battle cruiser if you examine the following figures _Queen Elizabeth_ (super-Dreadnought).--Length, 620 feet; tonnage, 27,500; horse-power, 28,000; speed per hour, 25 knots;[92] armour, belt of 13½ inch thickness; armament, eight 15-inch guns and sixteen 6-inch guns. _Lion_ (battle cruiser).--Length, 660 feet; tonnage, 26,350; horse-power, 70,000; speed per hour, 31 knots; armour, belt of 9¾ inch thickness; armament, eight 13.5-inch guns and sixteen 4-inch guns. The _Lion_, _Tiger_, _Queen Mary_, and _Princess Royal_ are the four most powerful battle cruisers in existence. Cruisers, of which we possessed 121 when war broke out, are the fighting scouts of the Fleet. What are called armoured cruisers, such as the unfortunate _Cressy_, _Aboukir_, and _Hogue_, are protected by belts of armour plate, varying from 6 inches to 8 inches in thickness. Protected cruisers have decks of armour plate instead of belts. The most modern cruisers, which are known as light armoured cruisers, have been described as "destroyers of destroyers." The light cruiser _Arethusa_, for example, has a belt of armour plating from 3 to 3½ inches thick. She is 410 feet long, displaces 3,600 tons, and has turbine engines that give her a speed of thirty knots. Like all the most modern warships, she consumes oil in place of coal. She mounts two 6-inch, six 4-inch, and four machine guns, with four torpedo tubes. Next in importance to the cruisers come the destroyers, of which we possessed 227 at the beginning of the war. These vessels may be said to correspond with the armoured motor car used by the Army. They are all built for speed, and most of them can steam over thirty miles an hour. The _Swift_, the largest destroyer in our Navy, has actually done over forty-four miles an hour; the _Tartar_, however, carries off the record, with a speed of nearly forty-six miles an hour. The _Swift_ displaces 2,170 tons, and is almost as big as the smallest of the light cruisers. Destroyers of the "L" class displace 965 tons, have a speed of about thirty-three miles an hour, and carry three 4-inch guns.