or a smaller terrella on the top of a larger; D its Southern pole. It
is manifest that D (the Southern pole) attracts a larger piece of iron, C,
than F (the Boreal pole) will be able to, if it is turned round downward to
the position D, toward the earth or the terrella in the Northern regions.

[Illustration]

Magneticks acquire strength through magneticks, if they are properly placed
according to their nature, in near neighbourhood and within the orbe of
virtue. Wherefore when a terrella is placed on the earth or on a terrella,
so that its Southern pole is turned round toward the Northern pole, its
Northern pole, however, turned away from the Northern pole, the influence
and strength of {107} its poles are increased. And so the Northern pole of
a terrella in such a position lifts up a larger spike than the Southern
pole, if the Southern pole is turned away. Similarly the Southern pole in a
proper and natural arrangement, acquiring strength from the earth or from a
larger terrella, attracts and retains larger rods of iron. In * the other
part of the terrestrial globe toward the South, as also in the Austral
portion of a terrella, the reasoning is converse; for the Southern pole of
the terrella being turned away is more robust, as also the Northern pole
when turned round. The more a region on the earth is distant from the
aequinoctial (as also in a larger terrella), the larger is the accession of
strength perceived; near the aequator, indeed, the difference is small, but
on the aequator itself null; at the poles finally it is greatest.

* * * * *

CHAP. XXXV.

On a Perpetual Motion Machine, mentioned
by authors, by means of the attraction
_of a loadstone_.

Cardan writes[183] that out of iron and the Herculean stone can be made a
perpetual motion machine; not that he himself had ever seen one, but only
conceived the idea from an account by Antonius de Fantis[184], of Treves.
Such a machine he describes, Book 9, _De Rerum Varietate_. But they have
been little practised in magnetick experiments who forge such things as
that. For no magnetick attraction can be greater (by any skill or by any
kind of instrument) than the retention. Things which are joined and those
which are approaching near are retained with a greater force than those
which are enticed and set in motion, and are moved; and that coition is, as
we have shown above, a motion of both, not an attraction of one. Such a
mach