variation.

* * * * *

{161} CHAP. V.

An island in Ocean does not change the variation[223], as
_neither do mines of loadstone_.

Islands, although they be more magnetick than the sea, yet do not change
the magnetick directions or variations. For since direction is a motion
derived from the power of the whole earth, not from the attraction of any
hill but from the disposing and turning power of the whole; so variation
(which is a perturbation of the direction) is an aberration of the real
turning power arising from the great inequalities of the earth, in
consequence of which it, of itself, slightly diverts movable magneticks
toward those which are the largest and the more powerful. The cause now
shown may suffice to explain that which some so wonder at about the Island
of Elba (and although this is productive of loadstone, yet the versorium
(or mariners' compass) makes no special inclination toward it whenever
vessels approach it in the Tyrrhenian sea); and the following causes are
also to be considered, viz.: that the virtue of smaller magnetick bodies
extends scarcely or not at all of itself beyond their own mines: for
variation does not occur because of attraction, as they would have it who
have imagined magnetick poles. Besides, magnetick mines are only agnate to
the true earth, not innate: hence the whole globe does not regard them, and
magneticks are not borne to them, as is demonstrated by the diagram of
eminences.

* * * * *

CHAP. VI.

That variation and direction arise from the disponent
_power of the earth, and from the natural magnetick tendency_
to rotation, not from attraction, or from coition,
_or from other occult cause_.

Owing to the loadstone being supposed (amongst the crowd of philosophizers)
to seize and drag, as it were, magnetick bodies; and since, in truth,
sciolists have remarked no other forces than those so oft besung of
attractive ones, they therefore deem every motion toward the north and
south to be caused by some alluring and inviting quality. But the
Englishman, {162} Robert Norman, first strove to show that it is not caused
by attraction: wherefore, as if tending toward hidden principles, he
imagined a _point respective_[224], toward which the iron touched by a
loadstone would ever turn, not a _point attractive_; but in this he erred
greatly, although he effaced the former error about attraction. He,
however,