5,000 feet. The lines are so curved as to offer the least possible resistance to the air. It is made of rubberized cotton cloth. It has lobes of rubberized fabric to act as rudders. When the wind blows, the lobes, which are attached to the rear third of the balloon, fill with wind. When the air is calm, the lobes hang loosely.
The construction of the balloon makes it ride horizontally and almost directly above its moorings. It is released and drawn down again by a windlass mounted on a motor truck, so that it can be transported to any desired location. A special feature of the Caquot is the location of the balloonette or air chamber within the main body of the gas bag. To separate it from the gas chamber, a diaphragm of rubberized cotton cloth is used. There is no air in the balloonette when it is first fully inflated at what is practically the ground level, but as the balloon ascends the wind blows into the balloonette through a scoop placed under the nose of the balloon. This forces up the balloonette and compensates for the inevitable leakage of gas from the envelope.
The average life of a kite balloon on an active war front was only fifteen days, but it did valuable work while it lasted. So anxious were the Germans to destroy them that they gave an aviator who brought one down a credit equivalent to the one bestowed for 1½ planes destroyed.
The scouting plane and the kite balloon represent the defensive feature of aviation. But it was soon discovered that the air service could also be made a formidable weapon of offense. Machine guns were furnished that were so synchronized that they shot through the blades of the propeller. Aerial squadrons were organized that wheeled and dove and rose in accordance with a system of tactics as precise as those on land and sea. There were Homeric battles in the sky, in which as many as forty or fifty planes might be engaged at once. Rewards were offered for those who brought down the greatest number of enemy machines and the coveted title of "ace" was bestowed upon the airman who had the attested destruction of five or more planes to his credit. Supremacy in the air was eagerly sought for by both sides, for it meant that one's own planes could hang over the enemy's front and watch his movements, while he was debarred from doing the same thing in return. Planes were constructed with armored protection to ward off the enemy bullets. Sometimes, instead of fighting with aerial competitors, a daring aviator would swoop down near the ground and rain machine-gun bullets on a marching detachment of the foe. The keen rivalry between the aerial enemies stimulated the invention of devices that would increase the effectiveness of the service. Chief among these was the wireless telephone, that enabled the aviator to
