“In these hours of trial, a smart Englishman invented a motor-driven balloon called a Blimp. It’s a mystery to me why they named it a Blimp. But, even with such a modern name, the Blimp could certainly scout for German submarines—the U-Boats. Whenever a Blimp found a U-Boat it would send a wireless message to a ship called a Submarine Destroyer which would chase the submarine and sink it.” [Illustration: A GREAT BATTLE IN WHICH THE AMAZING AIR FLEETS OF THE SEA TAKE PART] [Illustration: BOMB SPLITS ZEPPELIN IN HALF] “What I can’t understand,” said Tom thoughtfully, “is why they need a Blimp or an aeroplane to find U-Boats? Why can’t the Submarine Destroyers seek out the U-Boats for themselves?” “Yes, Uncle Sam, please explain that,” said Jack. “I’ll gladly tell you the reason,” said Uncle Sam. “You know that you can’t see through a window from the outside when the sun shines on it. It is the same on the sea. When the light shines on the water, it is impossible to see beneath the waves. But when an aviator is high overhead the light is not reflected in his eyes. Therefore, he is able to see twenty, thirty, and, sometimes, a hundred feet under the surface of the water. Furthermore, a man high in the air can look around and see more than the man below. “Now, I’ll start where I left off. I shall have to hurry along, as it is getting late. Since the early days of the great World War, many new inventions have made sea flying the marvel of the age. Suppose I tell you boys of a great battle in which the amazing air fleets of the sea take part. “Two hostile fleets of warships steam defiantly toward each other. How proudly their banners flaunt gay colors in the breeze! How boldly their stately bows plough through the sea! How grim, how stern their gray sides reflect the sunlight! Ere the day is over, many, many ships of these grand fleets will lie on the ocean floor. Many others will stagger to home ports—battered wrecks. “High over the enemy fleet are their Zeppelins, floating lazily with the clouds. Over our warships, darting here and there, are the ‘eyes’ of the fleet—our seaplanes. It won’t be long before the Zeppelins, the hostile aeroplanes, and our seaplanes are clinched in a struggle to death. [Illustration: THE DEPTH BOMB DESTROYS A U-BOAT] [Illustration] [Illustration: A MASS OF WRECKAGE THAT STRIKES THE DECK OF ONE OF OUR WARSHIPS]