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 i drawn to the East or West of the Correct Magnetic North, as shewn on the fixed card. |