WHY THE NORTH POLE OF ONE LODESTONE ATTRACTS THE SOUTH POLE OF ANOTHER
AND VICE VERSA
As already stated, the north pole of one lodestone attracts the south
pole of another and conversely; in this case the virtue of the stronger
becomes active, whilst that of the weaker becomes obedient or passive. I
consider the following to be the cause of this phenomenon: the active
agent requires a passive subject, not merely to be joined to it, but
also to be united with it, so that the two make but one by nature. In
the case of this wonderful lodestone this may be shown in the following
manner: Take a lodestone which you may call _A D_, in which _A_ is the
north pole and _D_ the south; cut this stone into two parts, so that you
may have two distinct stones; place the stone having the pole _A_ so
that it may float on water and you will observe that _A_ turns towards
the north as before; the breaking did not destroy the properties of the
parts of the stone, since it is homogeneous; hence it follows that the
part of the stone at the point of fracture, which may be marked _B_,
must be a south pole; this broken part of which we are now speaking may
be called _A B_. The other, which contains _D_, should then be placed so
as to float on water, when you will see _D_ point towards the south
because it is a south pole; but the other end at the point of fracture,
lettered _C_, will be a north pole; this stone may now be named _C D_.
If we consider the first stone as the active agent, then the second, or
_C D_, will be the passive subject. You will also notice that the ends
of the two stones which before their separation were together, after
breaking will become one a north pole and the other a south pole. If now
these same broken portions are brought near each other, one will attract
the other, so that they will again be joined at the points _B_ and _C_,
where the fracture occurred. Thus, by natural instinct, one single stone
will be formed as before. This may be demonstrated fully by cementing
the parts together, when the same effects will be produced as before the
stone was broken. As you will perceive from this experiment, the active
agent desires to become one with the passive subject because of the
similarity that exists between them. Hence _C_, being a north pole, must
be brought close to _B_, so that the agent and its subject may form one
and the same straight line in the order _A B_, _C D_ and _B_ and _C_
being at the same point. In this union the identity of the extreme parts
is retained and preserved just as they were at first; for _A_ is the
north pole in the entire line as it was in the divided one; so also _D_
is the south pole as it was in the divided passive subject, but _B_ and
_C_ have been made effectually into one. In the same way it happens that
if _A_ be joined to _D_ so as to make the two lines one, in virtue of
this union due to attraction in the order _C D A B_, then _A_ and _D_
will constitute but one point, the identity of the extreme parts will
remain unchanged just as they were before being brought together, for
_C_ is a north pole and _B_ a south, as during their separation. If you
proceed in a different fashion, this identity or similarity of parts
will not be preserved; for you will perceive that if _C_, a north pole,
be joined to _A_, a north pole, contrary to the demonstrated truth, and
from these two lines a single one, _B A C D_, is formed, as _D_ was a
south pole before the parts were united, it is then necessary that the
other extremity should be a north pole, and as _B_ is a south pole, the
identity of the parts of the former similarity is destroyed. If you make
_B_ the south pole as it was before they united, then _D_ must become
north, though it was south in the original stone; in this way neither
the identity nor similarity of parts is preserved. It is becoming that
when the two are united into one, they should bear the same likeness as
the agent, otherwise nature would be called upon to do what is
impossible. The same incongruity would occur if you were to join _B_
with _D_ so as to make the line _A B D C_, as is plain to any person who
reflects a moment. Nature, therefore, aims at being and also at acting
in the best manner possible; it selects the former motion and order
rather than the second because the identity is better preserved. From
all this it is evident why the north pole attracts the south and
conversely, and also why the south pole does not attract the south pole
and the north pole does not attract the north.