*
The Centre of the Magnetick Virtues in the earth
is the centre of the earth; and in a terrella
_is the centre of the stone_.
Rays of magnetick virtue spread out in every direction in an orbe; the
centre of this orbe is not at the pole (as Baptista Porta reckons, Chap.
22), but in the centre of the stone and of the terrella. So also the centre
of the earth is the centre of the magnetick motions of the earth; though
magneticks are not borne directly toward the centre by magnetical motion,
except when they are attracted by the true pole. For since the formal {96}
power of the stone and of the earth does not promote anything but the unity
and conformity of disjoined bodies, it comes about that everywhere at an
equal distance from the centre or from the circumference, just as it seems
to attract perpendicularly at one place, so at another it is able even to
dispose and to turn, provided the stone is not uneven in virtue. For if at
the distance C from the pole D the stone is able to allure a versorium, *
at an equally long interval above the æquator at A that stone can also
direct and turn the versorium. So the very centre and middle of the
terrella is the centre of its virtue, and from this to the circumference of
the orbe (at equal intervals on every side) its magnetick virtues are
emitted.
[Illustration]
* * * * *