The earth-inductor compass for airplanes, as developed at the Bureau of Standards contains several novel features:1. A null method is used for the indications. As long as the ship holds the prescribed course, the needle of the indicating galvanometer reads zero. A deviation from the course on either side is accompanied by a corresponding movement of the needle, which thus acts as a turn-indicator. 2. An iron core is used in the indicator, enabling the instrument to be designed of a small size.3. Rolling and pitching errors are eliminated by a specially damped gimbal suspension.4. A means is provided of distinguishing between north and south, or, in general, between any two opposite bearings.5. A distant electrical control is used, by means of which the inductor can be located at a distance from the engine, and the course-setting device and indicator be located at the instrument board.