When the airship came to turn a corner it was apt to “skid.” It slid from its balance, owing to the change in its course against the currents of air. The Wrights overcame this by having the planes of their machine warp at the same instant that the rudder shifts the course, by this raising one wing and lowering the other, so that the aeroplane cants over and makes the circle leaning against the wind, on the same principle that a bicycler takes a curve on an angle instead of riding upright. The problems of balance and of turning corners were therefore both met and solved by warping the planes to meet the conditions of the airship’s contact with the wind. One of the chief reasons for the Wrights’ success was that they had studied their subject long and faithfully before they tried to fly. They had worked with their gliders several years, and had made new calculations of the changing angles and currents of air. They had been in no hurry, and when they built their first real airship they made use of all the principles of aerodynamics that they had discovered. They knew that their machine would fly before they tried it, because they knew exactly what its various surfaces would do in the air. The propeller was the only part of their airship they had not studied when they began to build. When they found that they could not use the figures that had governed the construction of marine propellers they set to work to solve this problem in the same thoroughgoing way. They mastered it, and their success with their propeller is the feature of their airship in which they take the greatest pride. The first official statement of their progress in flying was made in letters of the Wrights in the _Aerophile_ in 1905, and to the Aero Club of America in 1906. These declared that they had begun actual flight with a motor-driven aeroplane on December 17, 1903, had then spent the year 1904 in experimenting with flights in circular courses, and had so learned the proper methods of control of the planes by 1905 that they had at last made continuous flights of eleven, twelve, fifteen, twenty, twenty-one, and twenty-four miles, at a speed of about thirty-eight miles an hour, and had been able to alight safely in each instance, ready to fly again as soon as their fuel was replenished. Until that date the inventors had been singularly successful in keeping their experiments from public knowledge. They had reached agreements with the farmers who lived near their field outside Dayton, and with the local newspapers, that no notice should be taken of their flights. But finally one of their flights attracted so much attention that a score of men appeared with cameras, and the Wrights decided that it was time to stop their experiments. They dismantled their machines, made public statements of what they had accomplished, and started to negotiate with various governments for the purchase of their aeroplanes for use in war.