To the battle-plane fell the task of clearing the air of the enemy. If the enemy's battle-planes were disposed of, his bombing-planes, his spotters, and his scouts could not operate, and he would be blind. And so each side tried to beat out the other with speedier, more powerful, and more numerous battle-planes. Fast double-seaters were built with guns mounted so that they could turn in any direction. THE FLYING TANK The Germans actually built an armored battle-plane known as the flying tank. It was a two-seater intended mainly for attacking infantry and was provided with two machine-guns that pointed down through the floor of the fuselage. A third gun mounted on a revolving wooden ring could be used to fight off hostile planes. The bottom and sides of the fuselage or body of the airplane from the gunner's cockpit forward were sheathed with plates of steel armor. The machine was a rather cumbersome craft and did not prove very successful. A flying tank was brought down within the American lines just before the signing of the armistice. AMERICA'S HELP Our own contribution to the war in the air was considerable, but we had hardly started before the armistice brought the fighting to an end. Before we entered the war we did not give the airplane any very serious consideration. To be sure, we built a large number of airplanes for the British, but they were not good enough to be sent to the front; they were used merely as practice planes in the British training-schools. We knew that we were hopelessly outclassed, but we did not care very much. Then we stepped into the conflict. "What can we do to help?" we asked our allies, and their answer gave us a shock. "Airplanes!" they cried. "Build us airplanes--thousands of them--so that we can drive the enemy out of the air and blind his armies!" It took us a while to recover from our surprise, and then we realized why we had been asked to build airplanes. The reputation of the United States as a manufacturer of machinery had spread throughout the world. We Americans love to take hold of a machine and turn it out in big quantities. Our allies were sure that we could turn out first-class airplanes, and many of them, if we tried. Congress made an appropriation of six hundred and forty million dollars for aëronautics, and then things began to hum. A BIRTHDAY PRESENT TO THE NATION