That neither Lilienthal nor any other experimenter had ever tried any more adequate method to insure lateral balance struck Orville as surprising. Why, he asked himself, wouldn’t it be possible for the operator to vary the inclination of sections of the wings at the tips and thus obtain force for restoring balance from the difference in the lifts of the two opposite wing tips? That seems today an obvious enough idea, but no one had ever done anything about it before. Orville had hit on a fundamental principle. (Indeed, this principle later became the basic claim of the original Wright patent, and the claim was sustained, as covering the idea of the aileron control, in all countries where the Wright patents were adjudicated.) Orville made a rough sketch of a wing, showing a stationary section at the center, consisting of approximately one-third of the wing, measured from tip to tip, with two adjustable sections, one at either side. These sections were carried on shafts interconnected by cogs mounted on the center section and extending toward the wing tips. The movement of a lever attached to one of the shafts would cause one wing section to rotate in one direction while the other wing would turn in the opposite direction. Thus a greater lift could be obtained on whichever side it was needed. The Wrights soon saw, however, that for two reasons this particular design did not provide a good structure for a gliding machine. First, with two-thirds of the entire weight of the machine and operator carried by the two shafts, the structure would be weak; and, second, with the ends of the wings free to turn about the shafts, there would not be enough rigidity for a machine that would have to be toted about. Then one night, some five or six weeks later, Wilbur came home from the bicycle shop, to tell Orville enthusiastically of an idea he had hit upon. A customer had dropped in to buy an inner tube for a tire. Wilbur had taken the tube from the pasteboard box it came in and was toying with the box while talking to the customer. As he twisted the box he observed that though the vertical sides were rigid endwise, the top and bottom sides could be twisted to have different angles at the opposite ends. Why, he thought, couldn’t the wings of a gliding machine be warped from one end to the other in this same way? Thus the wings could be put at a greater angle at one side than at the other, without structural weakness. That plan seemed so satisfactory that the Wrights did not look for or consider any other method.