Page:My Airships.djvu/156

 per minute, I realised, from a fixed point, a traction effort of 55 kilogrammes (120 lbs.). Indeed, the propeller turned with such force that I took pneumonia in its current of cold air. I betook myself to Nice for the pneumonia, and there, while convalescing, an idea came to me. This new idea took the form of my first true air-ship keel. In a small carpenter shop at Nice I worked it out with my own hands—a long, triangular-sectioned pine framework of great lightness and rigidity. Though 18 metres (59$\tfrac{1}{2}$ feet) in length it weighed only 41 kilogrammes (90 lbs.). Its joints were in aluminium, and, to secure its lightness and rigidity, to cause it to offer less resistance to the air and make it less subject to hygrometric variations, it occurred to me to reinforce it with tightly-drawn piano wires instead of cords. Then what turned out to be an utterly new idea in aeronautics followed. I asked myself why I should not use this same piano wire for all my dirigible balloon suspensions in place of the cords and ropes used in all kinds of balloons up to this time. I did it, and the innovation turned out to be peculiarly valuable. These piano wires, $\tfrac{8}{10}$ths