A new kind of light craft--a sort of dwarf destroyer--grew up with the war. It is so light that it forms a class of its own--the featherweight class. Its proper name is the Coastal Motor Boat, or the C.M.B. for short. But the handy man knows it simply as the Scooter. The first scooters were only forty feet long, the next were fifty-five, the last were seventy. Everything about them is made as light as possible; so that they can skim along in about two feet of water at an outside speed of nearly fifty (land) miles an hour. They are really the thinnest of racing shells fitted with the strongest of lightweight engines. They are all armed with depth charges, which are bombs that go off under water at whatever depth you set them for when attacking submarines. The biggest scooters also carry torpedoes. The scooters did well in the war. Whenever the hovering aircraft had spotted a submarine they would call up the scooters, which raced in with their deadly depth charges. Even destroyers were attacked and torpedoed. One day a German destroyer off Dunkirk suddenly found itself surrounded by scooters which came in so close that a British officer had his cap blown off by the blast from a German gun. He and his scooter, however, both escaped and his torpedo sank the Hun. Fourthly, come the submarines, those sneaky vipers of the sea that seem made on purpose for the underhand tricks of ruthless Germans. Deadly against unarmed merchantmen, and very dangerous in some other ways, the submarine is slow under water, no match for even a destroyer on the surface, and "tender" to attack by gunfire, to bombs dropped from aircraft, to "sea-quaking" depth charges, and, of course, to ramming. We shall presently hear more about these inventions of the devil. [Illustration: Seaplane Returning after flight.]