CHAP. X.
Magnetick Meridians of the Earth.
eridians have been thought out by the
geographer, by means of which he might both distinguish the longitude and measure the latitude of each region. But the
magnetick meridians are infinite, running in the same direction also, through fixed and opposite limits on the æquator,
and through the poles themselves. On them also the magnetick latitude is measured, and declinations are reckoned from
them; and the fixed direction in them tends to the poles, unless it varies from some defect and the magnetick is
disturbed from the right way. What is commonly called a magnetick meridian is not really magnetick, nor is it really a
meridian, but it is understood to pass through the termini of the variation on the horizon. The variation is a depraved
deviation from a meridian, nor is it fixed and constant in various places on any meridian.