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Modern data seem to support the thesis (van Bemmelen, 1899) that the secular motion of the northern magnetic pole is a nearly linear oscillation. This oscillation is along the axis of a great magnetic anomaly in the arctic. Except for the constraint of the anomaly, the motion would probably be circular or quasi-circular, as suggested by the historical declination-dip curves.
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E. R. Hope (1957) studied this question.
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