SYSTEM OF FIXED AND MOVEABLE COMPASS CARDS FOR ASCERTAINING AND APPLYING THE DEVIATION OF THE COMPASS. From the "ELEMENTARY MANUAL for the DEVIATION of the COMPASS in IRON SHIPS;" by Captain F. J. EVANS, R. N., C. B., F.R.S. THE OUTER fixed card represents a Compass not affected by the iron of the ship:or the Horizon with the magnetic points and degrees marked on it. The INNER moveable card represents the Compass as affected by the iron of the ship; and the Deviation produced is called East or West, according as the North point of this Compass is drawn to the East or West of the Correct Magnetic North, as shewn on the fixed card. |