Then, after testing more than 200 wing designs and plane surfaces in their wind tunnel, the Wright Brothers found out how to figure correctly the amount of curve, or camber, that was essential to weight-carrying wings. They discovered, too, that before man could be flown through the air, he must have his wings attached firmly to a body or platform which was firm and controllable. The Wrights in their earliest experiments had realized that to be practical their machine must be built not only to fly in a straight line, but also in order that it could be steered to the right or to the left. One day, Orville was twisting a cardboard box in his hand when Wilbur noticed it. Immediately he saw the solution to the problem of steering their airplane. The result was a design which changed the _lift_ of either end of the wing by warping its surface. If one end of the wing was warped to give it more _lift_, the machine would _lift_ on that side and fall off into a turn. Thus the problem of steering was solved by the Wrights. [Illustration: THE WRIGHT BROTHERS’ EXPERIMENTAL GLIDER] FIRST FLIGHT After a year of exhaustive study and experiments with models in their wind tunnel, the Wright Brothers were ready to experiment with a man-carrying glider. With the thoroughness that was typical of every move of the Wrights, the brothers asked the government to let them have information on meteorological conditions all over the country. By studying the weather charts they were able to find a locality where there was a continual flow of wind. This would be nature’s wind tunnel where they could test their glider day after day. Through their study of the charts they found that the wind conditions at Kitty Hawk, on the North Carolina coast, seemed to offer the best possibilities for their glider test. Orville and Wilbur Wright began their experiments with a small man-carrying glider at Kitty Hawk in 1900. From that time until 1903 they made hundreds of successful glider flights and kept accurate records of each flight. They recorded wind velocity, angle of flight, duration of flight, time of day, temperature, humidity, and sky conditions overhead with the typical Wright attention to detail. Each year the Wrights constructed new gliders which embodied principles they had discovered for themselves during their flights at Kitty Hawk. Each glider was larger and had longer and narrower wings than the one before. During the fall of 1902 the brothers recorded nearly a thousand flights in a glider with a wingspan of thirty-two feet. It had a front elevator and a vertical tail which helped to maintain lateral stability.