course hath often been held concerning the * poles of the earth and of
the stone, and concerning the aequinoctial zone; whilst lately we have been
speaking about the declining of magneticks toward the earth and toward the
terrella, and the causes of it. But while by various and complicated
devices we have laboured long and hard to arrive at the cause of this
declination, we have by good fortune found out a new and admirable (beyond
the marvels of all virtues magnetical) science of the orbes themselves. For
such is the power of magnetick globes, that it is diffused and extended
into orbes outside the body itself, the form being carried beyond the
limits of the corporeal substance; and a mind diligently versed in this
study of nature will find the definite causes of the motions and
revolutions. The same powers of a terrella exist also within the whole orbe
of its power; and these orbes at any distance from the body of the terrella
have in themselves, in proportion to their diameter and the magnitude of
their circumference, their own limits of influences, or points wherein
magnetick bodies rotate; but they do not look toward the same part of the
terrella or the same point at any distance from the same (unless they be on
the axis of the orbes and of the terrella); but they always tend to those
points of their own orbes, which are distant by similar arcs from the
common axis of the orbes. As, for example, in the following diagram, we
show the body of a terrella, with its poles and aequator; and also a
versorium on three other concentrick orbes around the terrella at some
distance from it. In these orbes (as in all those which we may imagine
without end) the magnetick body or versorium conforms to its own orbe in
which it is located, and to its diameter and poles and aequator, not to
those of the terrella; and it is by them and according to the magnitude of
their orbes that the magnetick body is governed, rotated, and directed, in
any arc of that orbe, both while the centre of the magnetick body stands
still, and also while it moves along. And yet we do not mean that the
magnetick forms and orbes exist in air or water or in any medium that is
not magnetical; as if the air or the water were susceptible of them, or
were induced by them; for the forms are only effused and really subsist
when magnetick substances are there; whence a magnetick body is laid hold
of within the forces and limits of the orbes; and within the orbes
magnet