Some submarines have a gun on deck, but their real weapon is the torpedo. There is a picture of one on page 183. It is really a little warship in itself, with its own hull, propeller, rudders, engines, and a mass of gun-cotton in the place of guns. This explosive is stored in the head of the torpedo, which is provided with a striker-rod of steel. When this rod hits the target it is forced back and explodes a little charge, which in its turn explodes the gun-cotton which lies behind it. A torpedo is fired from a tube, and immediately it strikes the water its engines begin to work. It then rushes towards its target at the rate of forty or fifty miles an hour for a distance of three miles or more. By means of a very remarkable piece of apparatus, it is steered back to its line of fire if it should be turned out of its course. If the aim is sure, and the torpedo hits its mark, the gun-cotton explodes with such terrific force that it will sink or cripple the biggest ship afloat. On ordinary warships a torpedo can be fired from a tube either above or below water. The tube can be moved just like a gun, and so a correct aim can be taken. The tubes of a submarine, however, are all below water, and they are fixed so that the submarine itself must be moved into the right position before it can discharge a torpedo with correct aim. Submarines have been called, with good reason, "the deadliest things that keep the sea." With only the thin periscope showing above the waves, they can silently and secretly creep within range of a warship, and send off a torpedo on its deadly errand. To detect the thin periscope from the bridge of a warship is not easy, and during the present war several gallant ships have been taken unawares and sent to the bottom. * * * * * Now let me tell you the story of a submarine that failed. On the 9th of August a flotilla of German submarines was in the North Sea. Their narrow gray bodies were furrowing the waves at a speed of about fifteen knots an hour. On the little deck of each of them stood a commander, sweeping the horizon through powerful glasses for signs of the enemy. Down below men were standing by the motors, examining the gauges, filling the compressed air chambers, and making sure that the torpedoes were "ship-shape." Yonder is Submarine U 9. Suddenly her commander closes his glasses with a snap. He has sighted the funnels of British cruisers, and the hour of action has arrived. The long-expected signal rings out below, and the commander leaves the tiny deck and withdraws into the interior through a hatch, which is carefully closed behind him. He takes his place in the conning-tower, where, under his hand and eye, is all the apparatus needed for steering and controlling the boat.