Flying like ducks in the form of a spear-head and in groups of from 3 to 300 or more was inaugurated by the German ace of aces, the Baron Von Richthofen, who was credited with shooting down eighty Allied planes in the Great War. Before this, however, it was discovered that flying in pairs was more safe than flying alone. With the development of the wireless telephone the numbers in the formation were increased until, in October, 1918, the Americans made a raid on Waville with 350 machines in formations. These formations were called circuses, first because of the gaudy camouflage which covered the red baron and his German machines; often they placed decoys beneath clouds, and when an unsuspecting scout descended on the decoy, the circus dived on the scout. This was done by both sides, so that it became very unsafe to fly alone, or even in pairs, on the West Front. The flight commander’s machine was usually marked with a trailing colored streamer, and he usually flew at the apex of the spear-head. The second in command usually had his machine also specially marked, so that if anything happened to the leader he could take command. The commander often signalled by firing Very pistols. These same formations were also used for bombing and reconnaissance. Formation flying was also very useful for strafing the enemy on the ground during the last four drives of the Germans in 1918. Groups of six machines were used for this manœuvre with great effect. Whether or not formation flying will become popular in peace-times remains to be seen. In case of a crash of one machine the others could bring aid quickly, or carry the occupants to their original destination. CHAPTER XI AERIAL NAVIGATION ATMOSPHERIC CONDITIONS—WINDS AND THEIR WAYS—CLOUD FORMATIONS, NAMES, AND ALTITUDES Just as the navigator must know the sea, so the aviator must have a knowledge of the heavens and the basic principles of aerodynamics in order to become a successful pilot. Although the air is volatile like the water, the aviator flies through it as a fish moves through water. Therefore the aerial navigator must know enough about the medium through which he travels to know what to do in an emergency. Through a knowledge with the fundamental principles of meteorology the fliers may know what to expect in the form of disturbances to the atmosphere, and how to meet those conditions. For aeroplane flight a calm clear day is the best. Then eddies and storms are not encountered, although the air is never absolutely free from the former in some degree. Even a strong gale is not a hindrance to flying, as the United States aero-mail and hundreds of machines on the battle-fronts have repeatedly demonstrated. Mists, fogs, and low-hanging clouds are the greatest impediments to flying where the machines are not fitted up with wireless telephones or directional wireless. For first flights the early morning and late evening afford the calmest atmospheric conditions.