They started by carefully surveying the work of previous experimenters, such as Lilienthal and Chanute, and from the lesson of some of the failures of these pioneers evolved certain new principles which were embodied in their first glider, built in 1900. In the first place, instead of relying upon the shifting of the operator's body to obtain balance, which had proved too slow to be reliable, they fitted in front of the main supporting surfaces what we now call an 'elevator,' which could be flexed, to control the longitudinal balance, from where the operator lay prone upon the main supporting surfaces. The second main innovation which they incorporated in this first glider, and the principle of which is still used in every aeroplane in existence, was the attainment of lateral balance by warping the extremities of the main planes. The effect of warping or pulling down the extremity of the wing on one side was to increase its lift and so cause that side to rise. In the first two gliders this control was also used for steering to right and left. Both these methods of control were novel for other than model work, as previous experimenters, such as Lilienthal and Pilcher, had relied entirely upon moving the legs or shifting the position of the body to control the longitudinal and lateral motions of their gliders. For the main supporting surfaces of the glider the biplane system of Chanute's gliders was adopted with certain modifications, while the curve of the wings was founded upon the calculations of Lilienthal as to wind pressure and consequent lift of the plane. This first glider was tested on the Kill Devil Hill sand-hills in North Carolina in the summer of 1900 and proved at any rate the correctness of the principles of the front elevator and warping wings, though its designers were puzzled by the fact that the lift was less than they expected; whilst the 'drag'(as we call it), or resistance, was also considerably lower than their predictions. The 1901 machine was, in consequence, nearly doubled in area--the lifting surface being increased from 165 to 308 square feet--the first trial taking place on July 27th, 1901, again at Kill Devil Hill. It immediately appeared that something was wrong, as the machine dived straight to the ground, and it was only after the operator's position had been moved nearly a foot back from what had been calculated as the correct position that the machine would glide--and even then the elevator had to be used far more strongly than in the previous year's glider. After a good deal of thought the apparent solution of the trouble was finally found.