tached to the compass card; e, a pinion connecting the follow-up motor and the compass card. Fastened to the gear d is a fork f f'. If the prongs of the fork be moved nearer to or farther from e, the attached gear d is turned, and the connected phantom gear b is turned in the same direction. Such a displacement of the prongs of the fork can be produced by moving forward or back a nearly frictionless wheel g on the end of a screw h which is ro- tatable in a nut fastened to the compass frame.
Suppose that the meridian component of the ship's velocity is directed north. Then, the meridian seeking axis of the sensitive element will be deflected toward the west through an angle 51, depending upon the latitude, speed and course of the ship (124). Values of this angle for various conditions are given in tables. If no correction be made, the follow-up system will rotate the north-south line of the compass card through the same angle in the same direction.