Page:My Airships.djvu/86

 turns to the minute the propeller, which was attached directly to the motor shaft, might easily, if all went well, give the air-ship a speed of not less than 8 metres (26$\tfrac{1}{2}$ feet) per second. The rudder I made of silk, stretched over a triangular steel frame. There now remained nothing to devise but a system of shifting weights, which from the very first I saw would be indispensable. For this purpose I placed two bags of ballast, one fore and one aft, suspended from the balloon envelope by cords. By means of lighter cords each of these two weights could be drawn into the basket (see Fig. 3), thus shifting the centre of gravity of the whole system. Pulling in the fore weight would cause the stem