Map by Edmund Halley from 1701 showing the degree to which magnetic north (as read by compasses) var
Map by Edmund Halley from 1701 showing the degree to which magnetic north (as read by compasses) varies from the direction toward the North Pole. The thick line extending from the southeastern United States is the “line of no variation.” Halley personally traveled to make this map and hoped it would help sailors travel more accurately, but his own longitudinal readings were flawed. -- source link
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