Abstract
Some years since I published in these Transactions, (Numb. 148.) a Theory of the Variation of the Magnetical Compass, wherein having collected as many Observations as at that time I could procure, and having carefully compared them together, I came at length to this general conclusion, That the Globe of the Earth might be supposed to be on great Magnet, having four Magnetical Poles or Points of Attraction, near each Pole of the Equator two :

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