“Then, quick as a flash, our men rush in and capture the trench before enemy reinforcements come up. The courageous aviators are wildly cheered but haven’t time now to listen to the praise; they must go up in the air again to protect their comrades from enemy aeroplanes, which lurk everywhere waiting for a chance to drop bombs.” “By the way, Uncle Sam,” asked Jack, “why do aviators wear such heavy clothing?” [Illustration: JUST BEFORE THE BATTLE] “It must be very cold up in the air,” thought Tom to himself, not saying anything for the first time. “It’s frightfully cold up above the clouds,” said Uncle Sam. “The higher you fly the colder it becomes. Up in the sky, I have often felt a temperature below zero, while down on the earth it was comfortable and warm. Later on in school, you boys will learn that the sun’s rays give very little heat until they reach the earth. I would explain the reason myself, but I want to go on with the story. “Our aviators are flying around in the sky about three miles above the earth when, all at once, the enemy’s machines dash into view. The two hostile air fleets see each other almost at the same time, and quickly prepare for action. A thrilling battle in the air is at hand. “Our machines are outnumbered, but that does not deter us. ‘Rat-a-tat-tat,’ shrieks one of our machine guns. One of the foe is put out of action. His machine in flames, he falls dizzily to earth. Marvelous flying is now going on. One of our men loops-the-loop to get into position. An enemy aviator backs up his machine in mid-air: then dives down headlong a thousand feet. Swiftly he rights himself and speeds up firing right, left, and straight ahead. We have a hard time dodging that dangerous fellow. [Illustration: WE POUNCE ON THE BIG ENEMY BATTLEPLANE] “A big enemy battleplane gets separated from the group. In just two seconds two of our force pounce upon it. The huge machine battles skillfully for a while. Then we force it into a bad position, and rain upon it a terrible storm of bullets from our machine guns. The big battleplane goes down, but fighting to the last. “Night approaches and envelops the earth with a blanket of darkness. Powerful searchlights from below, each of which is a wonderful instrument, scan the heavens with beams of ghostly white and yellow. The aeroplanes still struggle. The constant flashes from the bursting shells are even more terrible than in the day time. The scene is still more hideous when an unfortunate aviator takes the fatal plunge, his machine ablaze. One of our fine biplanes makes a mistake and gets right in line with an enemy’s gun. The foe’s machine-gun bullets penetrate its gasoline tank. It explodes in mid-air, and the biplane rushes to earth in a roaring blaze.” “Who wins this great battle?” broke in Tom. “Well, I’m getting to that now,” said Uncle Sam. “Tom, you ought to be ashamed of yourself. You have done nothing but interrupt during the whole story,” declared Jack.