FIG. G-10. Gyrocompass. (a) A gyroscope tends to maintain its orientation in space, making it appear to change direction as seen from the rotating Earth. (b) A weight on the vertical circle makes a gyroscope into a gyrocompass. Tilt of the gyroscope axis because of the Earth’s rotation tends to raise the weight, thus exerting a torque that makes the gyroscope precess unless the axis is aligned parallel to the Earth’s axis. This ‘‘meridian-seeking ability’’ is the essence of a gyrocompass.