They began coasting down the air from the tops of sand dunes, and after the first few glides were able to slide three hundred feet through the air against a wind blowing twenty-seven miles an hour. The reason their glider flights were made against the wind was because the wind passing swiftly under the planes had the same effect as if the machine was moving forward at a good clip, for the faster the machine moves, or the faster the air passes under it, the easier it remains aloft. In other words, no one part of the air was called upon to support the planes for any length of time, but each part supported the planes for a very short time. For instance, if you are skating on thin ice you run much less danger of breaking through if you skate very fast, because no one part of the ice is called upon to support you for long. In 1902 the Wright brothers were approaching their goal. Slowly and with rare patience they were accumulating and tabulating all the different things different kinds of planes would do under different circumstances. In the fall of that year they made about one thousand gliding flights, several of which carried them six hundred feet or more. Others were made in high winds and showed the inventors that their control devices were all right. The next year, 1903, which always will be remembered as the banner one in the history of aviation, the brothers, confident that they were about to succeed in their long search for the secret of the birds, continued their soaring or gliding. Several times they remained aloft more than a minute, above one spot, supported by a high, steady wind passing under their planes. "Little wonder," wrote the Wright brothers a few years, later, "that our unscientific assistant should think the only thing needed to keep it indefinitely in the air would be a coat of feathers to make it light." What the inventors did to keep their biplane glider in the air indefinitely, however, was to add several hundred pounds to the weight in the shape of a sixteen-horsepower gasoline motor. The total weight of the machine when ready to fly was 750 pounds. Every phase of the problem had been worked out in detail--all the calculations gone over and proved both by figures and by actual test. The planes, rudders, and propellers had been designed by mathematical calculations and practical tests.