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.
wing 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, Robert
Norman, first strove to show that it is not caused by attraction: wherefore, as if tending toward hidden principles, he
imagined a point respective224, 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, demonstrates his opinion in this way:
Let there be a round vessel filled with water: in the middle of the surface of the water place a slender iron wire on
a perfectly round cork, so that it may just float in æquilibrium on the water; let the wire be previously touched by a
magnet, so that it may more readily show the point of variation, the point D as it were: and let it remain on the surface
for some time. It is demonstrable that the wire together with the cork is not moved to the side D of the vessel: which it
would do if an attraction came to the iron wire by D: and the cork would be moved out of its place. This assertion of the
Englishman, Robert Norman, is plausible and appears to do away with attraction because the iron remains on the water not
moving about, as well in a direction toward the pole itself (if the direction be true) as in a variation or altered
direction; and it is moved about its own centre without any transference to the edge of the vessel. But direction does
not arise from attraction, but from the disposing and turning power which exists in the whole earth, not in the pole or
in some other attracting part of the stone, or in any mass rising above the periphery of the true circle so that a
variation
should occur because of the attraction of that mass. Moreover, it is the directing power of the loadstone and iron and
its natural power of turning around the centre which cause the motion of direction, and of conformation, in which is
included also the motion of the dip. And the terrestrial pole does not attract as if the terrene force were implanted
only in the pole, for the magnetick force exists in the whole, although it predominates and excels at the pole. Wherefore
that the cork should rest quiescent in the middle and that the iron excited by a loadstone should not be moved toward the
side of the vessel are agreeable to and in conformity with the magnetick nature, as is
demonstrated by a terrella: for an iron spike placed on the stone at C clings on at C, and is not pulled * further away by the pole A, or by the parts near
the pole: hence it persists at D, and takes a direction toward the pole A; nevertheless it clings on at D and dips also
at D in virtue of that turning power by which it conforms itself to the terrella: of which we will say more in the part
On Declination.