Magnetick Meridians of the Earth.
Meridians 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.
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{80} CHAP. XI.
Parallels.
In parallel circles the same strength and equal power are perceived
everywhere, when various magneticks are placed on one and the same parallel
either on the earth or on a terrella. For they are distant from the poles
by equal intervals and have equal tendencies of declination, and they are
attracted and held, and they come together with like forces; just as those
regions which are situated under the same parallel, even if they differ in
longitude, yet we say possess the same quantity of daylight and a climate
equally tempered.
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