Also magnetick bodies of iron, if alike in all respects, * come together
when excited with similar incitation.
Furthermore, bodies of iron not excited by a * loadstone, if they are alike
and not weighed down by their bulk, move towards one another with equal
motion.
Two loadstones, disposed on the surface of some water in {100} suitable
skiffs, if they are drawn up suitably within their orbes of virtue, incite
one another mutually to an embrace. So a proportionate * piece of iron in
one skiff hurries with the same speed towards the loadstone as the
loadstone itself in its boat strives towards the iron. From their own
positions, indeed, they are so borne together, that they are joined and
come to rest at length in the middle of the space. Two iron wires
magnetically excited, floating in water by means of * suitable pieces of
cork, strive to touch and mutually strike one another with their
corresponding ends, and are conjoined.
Coition is firmer and swifter than repulsion and separation in * equal
magnetick substances. That magnetick substances are more sluggishly
repelled than they are attracted is manifest in all magnetical experiments
in the case of stones floating on water in suitable skiffs; also in the
case of iron wires or rods swimming (transfixed through corks) and well
excited by a loadstone, and in the case of versoria. This comes about
because, though there is one faculty of coition, another of conformation or
disposition, repulsion and aversion is caused merely by something
disposing; on the other hand, the coming together is by a mutual alluring
to contact and a disposing, that is, by a double vigour.
A disponent vigour is often only the precursor of coition, in order that
the bodies may stand conveniently for one another before conjunction;
wherefore also they are turned round to the corresponding ends, if they can
[not][181] reach them through the hindrances.
[Illustration]
If a loadstone be divided through a meridian into two equal parts, the
separate parts mutually repel one another, the poles being * placed
directly opposite one another at a convenient and equal distance. They
repel one another also with a greater velocity than when pole is put
opposite pole incongruously. Just as the part B of the loadstone, placed
almost opposite the part A, repels it floating in its skiff, because D
turns away from F, and E from C; but if B is exactly joined with A again,
they agree and become one body {101} magnetical; but in proximity they
raise enmities. But if one part of the stone is turned round, so that C
faces D and F faces E, then A pursues B within its orbe until they are
united.
The Southern parts of the stone avoid the Southern parts, and the Northern
parts the Northern. Nevertheless, if by force you move up the Southern cusp
of a piece of iron too near the Southern part of the stone, the cusp is
seized and both are linked together in friendly embraces: because it
immediately reverses the implanted verticity of the iron, and it is changed
by the presence of the more powerful stone, which is more constant in its
forces than the iron. For they come together according to their nature, if
by reversal and mutation true conformity is produced, and just coition, as
also regular direction. Loadstones of the same shape, size, and vigour,
attract one another mutually with like efficacy, and in the opposite
position repel one another mutually with a like vigour.
Iron rods not touched, though alike and equal, do yet often act * upon one
another with different forces; because as the reasons of their acquired
verticity, also of their stability and vigour, are different, so the more
strongly they are excited, the more vigorously do they incite.
Pieces of iron excited by one and the same pole mutually repel * one
another by those ends at which they were excited; then also the opposite
ends to those in these iron pieces raise enmities one to another.
In versoria whose cusps have been rubbed, but not their cross-ends, * the
crosses mutually repel one another, but weakly and in proportion to their
length.
In like versoria the cusps, having been touched by the same * pole of the
loadstone, attract the cross-ends with equal strength.
In a somewhat long versorium the cross-end is attracted rather * weakly by
the cusp of a shorter iron versorium; the cross of the shorter more
strongly by the cusp of the longer, because the cross of the longer
versorium has a weak verticity, but the cusp has a stronger.
The cusp of a longer versorium drives away the cusp of a * shorter one more
vehemently than the cusp of the shorter the cusp of the longer, if the one
is free upon a pin, and the other is held in the hand; for though both were
equally excited by the same loadstone, yet the longer one is stronger at
its cusp on account of its greater mass.
The Southern end of an iron rod which is not excited attracts * the
Northern, and the Northern the Southern; moreover, also the Southern parts
repel the Southern, and the Northern the Northern.
If magnetick substances are divided or in any way broken in pieces, each
part has a Northern and a Southern end.
{102} A versorium is moved as far off by a loadstone when an obstacle * is
put in the way, as through air and an open medium.
Rods rubbed upon the pole of a stone strive after the same pole * and
follow it. Therefore Baptista Porta errs when he says, chapter 40[182], "If
you put that part to it from which it received its force, it will not
endure it, but drives it from it, and draws to it the contrary and opposite
part."
The principles of turning round and inclining are the same in the case of
loadstone to loadstone, of loadstone to iron, of iron also to iron.
When magnetick substances which have been separated by force and dissected
into parts flow together into a true union and are suitably connected, the
body becomes one, and one united virtue, nor have they diverse ends.
The separate parts assume two opposite poles, if the division has * not
been made along a parallel: if the division has been made along a parallel,
they are able to retain one pole in the same site as before.
Pieces of iron which have been rubbed and excited by a loadstone are more
surely and swiftly seized by a loadstone at fitting ends than such as have
not been rubbed.
If a spike is set up on the pole of a loadstone, a spike or style * of iron
placed on the upper end is strongly cemented to it, and draws away the
erect spike from the terrella when motion is made.
If to the lower end of the erect spike the end of another spike * is
applied, it does not cohære with it, nor do they unite together.
As a rod of iron draws away a piece of iron from a terrella, so is it also
with a minute loadstone and a lesser terrella, though weaker in strength.
[Illustration]
The piece of iron C comes into conjunction with the terrella A, and the
vigour in it is magnetically exalted and excited, both in the adjoining end
and in the other also which is turned away through {103} its conjunction
with the terrella. The end that is turned away also conceives vigour from
the loadstone B; likewise the pole D of that loadstone is powerful on
account of its suitable aspect and the nearness of the pole E of the
terrella. Several causes therefore concur why the piece of iron C should
cleave to the terrella B, to which it is joined more firmly than to the
terrella A; the vigour excited in the rod, the vigour also excited in the
stone B, and the strength implanted in B concur; therefore D is more firmly
cemented magnetically with C than E with C.
But if you were to turn the vertex F round to the iron C, C would not
adhære to F as formerly to D; for stones so arranged being within the orbe
of virtue are placed contrary to natural order; wherefore F does not
receive power from E.
Two loadstones or excited pieces of iron, duly cohæring, fly * asunder on
the approach of another more powerful loadstone or magnetized piece of
iron. Because the new-comer repels the other with its opposing face, and
dominates it, and ends the relationship of the two which were formerly
joined. So the forces of the other are lessened and succumb; but if it
conveniently could, being diverted of its association with the weaker, and
rolling round, it would turn about to the stronger. Wherefore also
magnetick bodies suspended in the air fall when a loadstone is brought near
them with an opposing face, not (as Baptista Porta teaches) because the
faculty of both those which were joined before grows faint and torpid, for
no face can be hostile to both the ends which cohære, but to one only; and
when the stronger loadstone, coming fresh with opposing face, impels this
further from it, it is put to flight by the friendly reception of the
former.
* * * * *