These two brothers, scientifically minded, started a bicycle shop, and bade fair to become ordinarily prosperous citizens of Dayton, much like their neighbors. They were, however, deeply interested in news from the world of science and invention, and when they read in 1896 that Lilienthal had been killed by a fall from his glider they began to wonder what were the real difficulties that must be overcome in flying. Further reading awakened a deep interest in the problem of the airship, and they worked upon it, at first as a scientific pastime, but soon in all seriousness. They built models in their workshop, and experimented with them. Then, in 1900, Wilbur wrote to his father that he was going on a holiday to a place in North Carolina called Kitty Hawk, to try a glider. The Wrights realized in 1900 that the only problem to be solved was that of equilibrium. Men had made aeroplanes that would support them in motion, and also engines that were light enough to drive the planes and carry their own weight and that of the aviator. But when the wind blew the aeroplane was as likely as not to capsize. Their study was how to keep the machine from turning over. The air does not blow in regular currents. Instead, near the earth, it is continually tossing up and down, and often whirling about in rotary masses. There is constant atmospheric turmoil, and the question is how to maintain a balance in these currents that bear the machine. Put in technical form it is how to make the centre of gravity coincide with the centre of air-pressure. The shifting of the air-currents means that the centre of air-pressure moves. The aeroplane is sailed at a slight angle to the direction in which it is heading, and the centre of air-pressure is on the forward surfaces of the machine. The wind strikes the front, but rarely touches the back of the plane, and so gains a great leverage that adds materially to its power to overturn the machine. As the wind veers continually it is easy to see the aviator’s difficulty in keeping track of this centre of pressure. Both Lilienthal and Chanute had tried to balance by shifting their weight, but this was extremely exhausting, and often could not be done in time to meet the changing currents. The Wrights realized that a more automatic method of meeting these changes must be found, and they worked it out by shifting the rudder and the surfaces of the airship as it met the air-currents.