The gyroscope has been applied for instance to railroad trains and has worked, experimentally at least, with remarkable success. By installing a gyroscope on a car running on a single track the car may be kept upright by the stabilizing force exerted by the revolving wheel. The same principle has been applied to steamships to prevent their rolling in heavy seas. The tipping of a car running on a single track, or of a ship at sea, is of course very much like the rolling of an aeroplane in flight; and it would seem that such a stabilizing device might solve the problem. The gyroscope has a serious disadvantage, however. Since it revolves at enormous speed any breakage would tend to throw the detached part to one side with dangerous force. In the case of the gyroscope used to steady ships at sea this force would be sufficient to send a piece of metal through the hull. On so delicate a craft as an aeroplane such an accident might readily prove disastrous. It has been found again in experiments with gyroscopes on steamers that the frames have been seriously strained, even when the gyroscope worked smoothly. When a ship rolls and pitches to the motion of the waves, it is of course under a great strain but this balances itself. When it is held in a rigid horizontal position the pitching and rolling exert an exaggerated strain on the hull. In one instance a vessel actually broke its back under such a strain and was lost. An air ship, being at best a very frail structure, could scarcely be expected to stand the strain which has wrecked a steel ship. At the recent Paris Aeronautical show several extremely ingenious combinations of the pendulum and gyroscope principles were illustrated. It is of course possible that some modified form of the gyroscope may solve the problem. A remarkable series of tests has been made this year in France with an automatic stability device based upon an entirely new principle. The rudders are operated automatically, in this case by a vertical fin opposed to the wind. As the pressure of the air varies, the rudder is forced up or down, thus bringing the aeroplane to an even keel without the assistance of the aviator. It is reported that model aeroplanes equipped with this device have been flown in three hundred experiments without a single accident.