agonic line

American  

noun

1. an imaginary line on the surface of the earth connecting all points at which the declination of the magnetic field of the earth is zero.

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agonic line British  

noun

1. an imaginary line on the surface of the earth connecting points of zero magnetic declination

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agonic line Scientific  

/ ā-gŏn′ĭk /

1. An imaginary line on the Earth's surface connecting points where the magnetic declination is zero. The agonic line is a line of longitude on which a compass will show true north, since where magnetic declination is zero, magnetic north coincides with geographic north.

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Etymology

Origin of agonic line

First recorded in 1860–65

Example Sentences

These two observations, one by Columbus and the other by Cabot, sufficed to determine the position of the agonic line, or line of no variation, for that locality and epoch.

From Project Gutenberg