Question
Define two magnetic elements of the earth.

Answer

Declination : The angle between the magnetic meridian and the geographic meridian at a place is called the declination at that place and is denoted by $\alpha$. The magnetic meridian of that earth may be due east or due west of its geographic meridian. Hence, it is expressed as $\alpha^{\circ}$ east or $\alpha^{\circ}$ west. In figure, < GOM, the declination is $\alpha^{\circ}$ east.
Inclination : This is the angle made by the magnetic field of the earth with the horizontal. It is generally denoted by denoted by $\delta$. In figure, < DOA is the angle of dip. The angle of dip at a place is measured by an instrument called dip circle, which has a compass needle that can rotate freely in a vertical plane.

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