MAGNETISM DURING THE SEVENTEENTH CENTURY HH Ricker III

“adored not only as the sole inventor of Magneticks, a new science to be added to the
Bulk of learning, but as the Father of the new Philosophy; Cartesius being but a builder upon
his experiments.” 28
The unfortunate fact that the foundations for field theory provided by Gilbert were not extended
or exploited by the English, is a mark against their scientific reputations. They were swept up in
the enthusiasm for a new anti-aristotelian mechanical approach and failed to see the truth within
the Gilbertian field theory.
The approach used by the English mechanizers of magnetism was not to build a mechanical
magnetic theory, that had already been done by Descartes and Gassendi, but to perform
experiments which supported the claims of these mechanistic theories against those of which
asserted the incorporeal action of the magnet. This negative approach was entirely successful,
but ultimately destructive towards the goal of a successful theory of magnetism. The significance
of the English approach lies in the body of magnetic experiments that was developed to refute
the incorporeal interpretation of magnetic action.
During the decade from 1650 to 1660, the English took aim at the incorporeal theories of
magnetism using the weakness which was previously noticed, the changes in magnetization due
to heating and mechanical deformation. This approach can be traced to Pierre Gassendi’s
Philosophiae Epicuri Syntagma, published in 1649, where Gassendi briefly notes that evidence
for the corpuscular theory of magnetism is provided by the decay of magnetic virtue with time,
its destruction by heat, and by the differences or variations exhibited in magnetic strength. The
idea was picked up by Walter Charleton who presented it as his first experimental proof that the
magnetic virtue was caused by a “corporeal efflux.” According to Charleton in the Physiologia
Epicuro-Gassendo-Charletonia published in 1654:
”The materiality of the magnetic virtue is inferrible likewise from hence, that it decays in
progress of time (as all Odours do) and is destroyed by fire, in a few minutes, and is capable of
Rarity and Density (whence it is more potent near at hand, than at the extremes of it[s] sphere)
all which are the proper and incommunicable Attributes of Corporeity.” 28
Henry Power, a physician from Halifax and a supporter of Descartes magnetic theory, took up
the challenge of extending Walter Charleton’s argument supporting materialistic magnetism by
producing new experiments. Following the new inductive method, during the years 1656 to 1659
he subjected magnets to a wide variety of harsh mechanical treatments. They were heated,
cooled, struck, stroked, bored, and drilled. Anything that would justify a mechanical explanation
was tried. The result was nine new demonstrations of the mechanical production of magnetism
which were contained in a book on magnetism entitled Experimental Philosophy, The Third
Book, Containing Experiments Magnetical: With a Confutation of Grandamicus, published under
the auspices of the Royal Society in 1663. The most persuasive of these was described in
Argument 8 as follows:
“Take a rod of Iron (or a Puncheon) as before; heat it red-hot, and according to the laws in its
refrigeration, you may endue this or that extreme with whether polarity you please; now
afterwards by striking it with a Hammer in the same posture that it was cooled in, you may much