Apart from governing the ascending or descending movement, there was the question of preventing a machine from slipping sideways; and this the Wrights solved ingeniously. They saw, of course, that when their glider lurched to one side or the other, they would need some power to tilt it back again. So they devised a system by which the plane-ends of their machine--being made flexible--might be warped, or caused to shift up and down. This action the operator controlled, as he lay across the lower plane, by a movement of cords, and its operation is shown in Fig. 29. The effect upon the machine may be described thus: should a wind-gust tilt down one plane-end, the “warp” upon that side of the machine was drawn down also, and the effect of this--seeing that it caused the plane to assume a steeper angle to the air and exercise a greater lift--was to raise the plane-ends that had been driven down by the gust. By a system of connecting the control cords, this balancing influence was made to act with double force; when one wing warped down, the other moved up; and, in this way, while the side of the machine tilted down was made to rise, the other plane-ends, which had been lifted, were made to descend. A dual righting influence was thus obtained. This system, which imitates the flexing movements made by a bird, was an important device; the Wrights patented it--combining the movement with an action of the rudder--and brought cases at law to enforce their rights. [Illustration: FIG. 29.--The Wright Wing-warp.] In the summer of 1900, with their first machine, the brothers went for experiments to Kitty Hawk, North Carolina. They had chosen this lonely settlement, located on a strip of land that divides Albemarle Sound from the Atlantic Ocean, because they hoped it would provide them with a strong, steady wind; there were also, fairly close to the settlement, suitable sand-hills for gliding. Upon the first day of their trials the wind was blowing at nearly 30 miles an hour, and they allowed the glider to rise as a kite. Flown in this way, it bore the weight of a man; but they were disappointed at the position it assumed when in the air. Its planes set themselves at an angle which was too steep, and it seemed to give less lifting power than they had expected. They tested their system of control, and found that the wing-warping for sideway balance acted extremely well, proving quicker and more certain than would the shifting from side to side of the operator’s body. The elevating plane was also efficient. [Illustration: FIG. 30.--Launching the Wright Glider.]