n relatively new effects could be produced by the loadstone.
He was more interested in what he could do with the magnet than in
explaining these effects. However, he discussed it at sufficient
length for one to find that his explanation of magnetic phenomena was
basically similar to that of his contemporary, St. Thomas.

Peregrinus based his discussion of the loadstone upon its nature and
analyzed magnetic phenomena in terms of the change of alteration. In
magnetic attraction, the nature of the iron is altered by having a new
quality impressed upon it,[26] and the loadstone is the agent that
makes the iron the same species as the stone.[27]

... Oportet enim quod illud quod iam conversum est ex duobus
in unum, sit in eadem specie cum agente; quod non esset, si
natura istud impossible eligeret.

This impressed similarity to the agent, Peregrinus realized, is not
a pole of the same polarity but one opposite to that of the inducing
pole. To produce this effect, the virtue of the stronger agent
dominates the weaker patient and impresses the virtue of the stronger
on the weaker so that they are made similar.[28]

... In cuius attractione, lapis fortioris virtutis agens est;
debilioris vero patiens.

A further instance of alteration occurs in the reversal of polarity of
magnetized iron when one brings two similar poles together. Again, the
stronger agent dominates the weaker patient and the iron is left with
a similarity to the last agent.[29]

... Causa huis est impressio ultimi agentis, confundentis et
alterantis virtutem primi.

In this assimilation of the agent to the patient, another effect is
produced: the agent not only desires to assimilate the patient to
itself, but to unite with it to become one and the same. Speaking of
the motion to come together, he says:[30]

Huius autem rei causam per hanc viam fieri existimo: agens
enim intendit suum patiens non solum sibi assimilare, sed
unire, ut ex agente et patiente fiat unum, per numerum. Et
hoc potes experiri in isto lapide mirabili in hunc modum....
Agens ergo, ut vides experimento, intendit suum paciens sibi
unire; hoc autem fit ratione similitudinis inter ea. Oportet
ergo ... virtute attractionis, fiat una linea, ex agente et
patiente, secundum hunc ordinem ...

The nature of the magnet, as an active cause, tends to enact, and
since it acts in the best manner in which it is able, it acts so as
to