1911 Encyclopædia Britannica/Declination
DECLINATION (from Lat. declinare, to decline), in magnetism the angle between true north and magnetic north, i.e. the variation between the true meridian and the magnetic meridian. In 1596 at London the angle of declination was 11° E. of N., in 1652 magnetic north was true north, in 1815 the magnetic needle pointed 241° W. of N., in 1891 18° W., in 1896 17° 56′ W. and in 1906 17° 45′. The angle is gradually diminishing and the declination will in time again be 0°, when it will slowly increase in an easterly direction, the north magnetic pole oscillating slowly around the North Pole. Regular daily changes of declination also occur. Magnetic storms cause irregular variations sometimes of one or two degrees. (See Magnetism, Terrestrial.)
In astronomy the declination is the angular distance, as seen from the earth, of a heavenly body from the celestial equator, thus corresponding with terrestrial latitude.