Today, in America, gliders are used for carrying mail. A plane towing a number of gliders reminds us of a tug towing a line barges on the Thames, or in a harbour. The gliders used in America for mail can be pulled off the ground by an airplane in full flight on its return journey.
The men who first experimented with sailplanes hoped to imitate the flight of birds. They had seen large birds remaining in the air fro long periods of time with wings outstretched but unmoving. They had noticed that these birds were able to gain height without making any effort.
In 1911 one of the Wright brothers, who had built a successful airplane in 1903, made a glider and fitted it with controls like those used in their plane. He stayed up in the air in this glider for nearly ten minutes.
Gliding did not make much progress until after the First World War. It then became a popular sport in Germany. Much was learnt about the use of air currents. It is a simple matter to launch a sailplane, either by using a catapult or by towing it behind an airplane and then releasing it. But if the air is still the sailplane will move in a downward path. A well-designed modern sailplane, flying at 50 feet per second, loses height at the rate of 2 feet per second. If there is no up-current of air, therefore, it can glide for a distance equal to twenty-five times its height above the ground. (259 words)
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1. mail: letters, etc., sent or delivered by post.
2. in full flight: while flying fast.
3. imitate: copy, act like.
4. gain: obtain; gain height: go to a greater height.
5. make an effort: try hard.
6. fitted it with controls: put controls into place in the glider.
7. It is a simple matter: It is quite easy.