The travel of the center of pressure on aeroplanes is from the center at 90 degrees, toward the front edge as the angle becomes smaller. The center of pressure on a curved surface is approximately at its center at 90 degrees, moves forward as the angle is decreased until a critical angle is reached, after which it reverses, and moves toward the rear edge. The critical angle varies for different shaped curves, but is generally reached at some angle between 12 and 18 degrees. With the angles used in gliding flight the travel will be between the center of the surface and a point one-third back from the front edge. The methods of construction used in our gliders are fully described in an article by Mr. Chanute in the _Revue des Sciences_ in 1903 (we do not remember the month) and in the specifications of our United States patent, No. 821,393. The ribs of our gliders were made of second growth ash, steamed and bent to shape. Selfridge replied in a few days saying he had been able to obtain a copy of the patent and would endeavor to get the other references the Wrights had supplied. The data must have been useful to the Aerial Experiment Association for early the following summer, Glenn Curtiss, “Director of Experiments” had a power-driven airplane, called the “June Bug,” in which he made a flight on July 4, 1908, at Hammondsport. That flight created the belief in the minds of many who were not fully informed that the Aerial Experiment Association must have done an amazing job of original research. This belief was encouraged by the fact that after the Aerial Experiment Association began building and experimenting with flying-machines, using much information they had obtained from the Wrights, they neglected, in public statements about their work, to so much as mention the Wright brothers. Soon after the report of the flight of the “June Bug,” there appeared in the press a statement that the Aerial Experiment Association was disbanding, and that Glenn H. Curtiss was going to engage in exhibition flying. That news led Orville Wright to send to Curtiss the following letter: I learn from the _Scientific American_ that your “June Bug” has movable surfaces at the tips of the wings, adjustable to different angles on the right and left sides for maintaining the lateral balance. In our letter to Lieutenant Selfridge of January 18th, replying to his of the 15th, in which he asked for information on the construction of flyers, we referred him to several publications containing descriptions of the structural features of our machines, and to our U. S. patent No. 821,393. We did not intend, of course, to give permission to use the patented features of our machine for exhibitions or in a commercial way.