"But our work is done. There is no doubt now about the fate of the U-boat. It is not necessary for one of the depth bombs actually to come in contact with the submerged craft to destroy it. When under water, a submarine's rigidity is multiplied. Its elasticity is next to nothing. An explosion as powerful as that of a depth bomb near it, is almost certain to cripple it if not destroy it. It is the same principle as that which kills fish in a pond when dynamite is exploded beneath the surface of the water. The shock is sufficient to kill the men in the U-boat, and so we glide along homeward, secure in the knowledge that even if our gunfire did not finish the enemy, the bombs have done the work. On the surface, we notice swarms of dead fish." THE HAWK-EYED AEROPLANE. The last wrinkle developed for submarine hunting was the aeroplane. Like a fish-hawk it can see its prey beneath the water by flying high in air. Another step just a bit in advance of aeroplane scouting for submarines is the use of a small dirigible for the same purpose. But the cleverest development of the aeroplane-submarine idea involved the use of seaplanes for the purpose of launching submarine torpedoes at enemy ships. Here's how this is practiced. As most folks know, the seaplane differs from the land-flying craft in that it rides on floats instead of wheels. These floats permit the seaplane to come to rest on the waves, and to launch itself again. Between these floats, which resemble a pair of broad home-made sleds, may be slung a torpedo. The same type of missile, this, that is used by the submarine and the destroyer--a long, cigar-shaped cylinder, operated by compressed air driving a propeller, and equipped with a warhead filled with guncotton. The torpedo is held by slings, delicately adjusted so that they can be released in an instant. The great seaplane, swinging the missile of death between its giant floats, climbs the skies in search of an enemy ship. From a distance of miles, perhaps, the seaplane looks like a gull. To the observer in the plane, however, sweeping the horizon with his binoculars, a ship is plainly and easily seen. NOT TO BE OUT-DISTANCED. Off in the distance is spied a ship suspected of being an enemy transport. It isn't hard to determine--the ship cannot steam away from them, no matter how swift its engines. A seaplane can go so fast that it makes the fastest torpedo boat destroyer look as if it were standing still. The attacked transport may try to bring its anti-aircraft guns to bear, if luckily it is equipped with them. Failing this, the soldiers will man the decks with their rifles ready. Then there is a duel of skill and daring between the men on the cruiser and the lone fighters in the seaplane.