244 NAVIGATIONAL COMPASSES
control magnets FF' on the sensitive element. Also, both the sensitive element and the compass card were deflected from the meridian through an angle S, in the counter-clockwise direction. The setting of the dial rotated the line connecting the follow-up coils CC' through an angle 61 in the counter-clockwise direction away from the line connecting the control magnets FF' without changing the direction of the north-south line of the compass card. The follow-up system immediately started to rotate the pinion e, thereby turning both the compass card and the phantom geared to it through the angle S, in the clockwise direction, that is, till the line connecting the follow-up coils CC' was brought again into coincidence with the line connecting the control magnets FF'. By this rotation of the compass card, the north-south line was brought into the meridian. The meridian-seeking axis of the sensitive element is still at an angle S, to the meridian.
145. Prevention of the Ballistic Deflection Error. - A gyrocompass will be without ballistic deflection error at the equator if the undamped period has a value given by (126). If the compass be moved to any other latitude X, the compass will continue to be without ballistic deflection error if