CHAPTER IX

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.