“An aviator’s most important duties are to take photographs of the enemy’s location and direct artillery fire. The aviator must seek out the enemy and learn their exact position. He must discover, if he can, about how many men and guns they have; how well they are fortified; how hard or easy it is to attack them. He makes many photographs and sketches which are valuable to his officers in planning an attack.” “You haven’t told us how the brave aviator directs artillery fire,” broke in Tom. “I’m getting to that now,” said Uncle Sam. “You know that there was a time when a man who fired a cannon could see his target. But now, a cannon, or the artillery, fires at a range of from six to thirty miles. No matter how big the target, it is impossible to see it from such a distance, especially when trees, mountains or fogs are in the way. Firing artillery is now a matter of calculation. Just where to shoot has to be figured out by means of maps, instruments, and mathematics. Quite often the figuring is not exactly right. The aviator must go up—bombs and shells bursting all around him—and discover if the guns are hitting the mark. When a shot doesn’t strike in the right place, the aviator sends directions by wireless for firing the next shell so that it will hit the enemy’s position and destroy it. [Illustration: SCOUTING OVER THE RUINED REGION BETWEEN THE LINES (NO MAN’S LAND)] [Illustration: BATTLEPLANES CONVOYING PHOTOGRAPHING AEROPLANES] “Not all the excitement is over the battle lines. One of the most thrilling experiences an aviator can have is to fight off enemy aeroplanes and Zeppelins when they come to drop bombs on a city or town. Cities liable to be raided by hostile machines are protected by lookout towers. As soon as the Zeppelins are sighted, the men in the towers toot shrill blasts on loud siren horns. At the signal of the horns every light in the attacked city is put out, and all the people rush into houses and cellars for safety. Big anti-Zeppelin guns are pointed skyward to fire destruction-dealing shells at the enemy overhead. “The brave aviators, who protect the city, start their machines and go up in the air to drive off the foe—amid the reek of fire and the scream of shot and shell. The battle is usually short. The swift defending aeroplanes, with their machine guns constantly spitting bullets, fight rings around the Zeppelins. The big guns on the ground send deadly missiles through many of the enemy airships. All of a sudden one bursts into flames. With a roar and a bang it hurtles to the earth. In the next moment, still another is hit. One of the doomed men saves himself by dropping off in a huge floating parachute. He is made prisoner the minute he touches ground. [Illustration: FIGHTING ZEPPELIN RAIDERS] [Illustration: TOOTING THE SIRENS OF WARNING]