Agonic Line

Agonic Line. The magnetic needle does not, as a rule, point to the true north. Thus, at London the declination from the true north is now about 18° to the westward. There are, however, certain points on the earth's surface where the magnetic and geographical meridians coincide, that is, where the needle points true north and south. These points lie on an imaginary line called the agonic line or line of no variation, which is of some importance in navigation. Roughly speaking, the western portion of this line traverses Hudson's Bay, Cape Hatteras, and the South Atlantic; the eastern portion crosses the White Sea, the Caspian Sea, the Indian Ocean, and the Great Australian Bight.