on the variation under the æquinoctial line, and near it.

i n the north the magnetick needle varies because of the boreal eminences of the continent; in the south because of the austral; at the æquator, if the regions on both sides were equal, there would be no variation. but because this rarely happens some variation is often observed under the æquator; and even at some distance from the æquator of three or 4 degrees toward the north, there may be a variation arising from the south, if those very wide and influential southern continents be somewhat near on one side.