Two months after the war started the first airplane was sent crashing to earth after a battle in the sky. The fight took place five thousand feet above the earth, between a French and a German machine. The German pilot was killed and the plane fell behind the French lines, carrying with it a Prussian nobleman who died before he could be pulled out of the wreckage. The war had been carried into the skies. But if scouts were to fight one another, they could not pay much attention to scouting and spotting and it began to be realized that there were four distinct classes of work for the airplane to do--scouting, artillery-spotting, battling, and bombing. Each called for special training and its own type of machine. As air fighting grew more specialized these classes were further subdivided, but we need not go into such refinements. AIR SCOUTS AND THEIR DANGERS The scouting-airplane usually carried two men, one to drive the machine and the other to make observations. The observer had to carry a camera, to take photographs of what lay below, and he was usually equipped with a wireless outfit, with which he could send important information back to his own base. The camera was sometimes fitted with a stock like that of a gun, so that it could be aimed from the shoulder. Some small cameras were shaped so that they could be held in the hand like a pistol and aimed over the side of the fuselage, or body, of the airplane; but the best work was done with large cameras fitted with telescopic lenses, or "telephoto" lenses, as they are called. Some of these were built into the airplane, with the lens opening down through the bottom of the fuselage. [Illustration: (C) Underwood & Underwood A Handley-Page Bombing Plane with One of its Wings Folded Back] The scouting-airplane carried a machine-gun, not for attack, but for defense. It had to be a quick climber and a good dodger, so that it could escape from an attacking plane. Usually it did not have to go very far into the enemy country, and it was provided with a large wing-spread, so that if anything happened to the engine, it could _volplane_, or glide back, to its own lines. As the scouting-planes were large, they offered a big target to anti-aircraft guns, and so the work of the air scout was to swoop down upon the enemy, when, of course, the machine would be traveling at high velocity, because it would have all the speed of falling added to that which its own propeller gave it. [Illustration: How an object dropped from the Woolworth Building would increase its speed in falling]