220 Natural philosophy
distance. The mysterious powers of magnets, what was more, had long
been traced to possession of a soul. Hale mentioned this had been the view
of Thales, cited by Aristotle in an early passage of De anitna? A principal
aim of Gilbert's De magnete (1601) the classic modern study of the
problem, was to show that the earth was a magnet, possessing 'anima', in
spite of being found below the moon.
8
A further advantage of magnets,
from the standpoint of a dabbler in these questions, was that an individual
could easily conduct his own research. The equipment necessary was
neither cumbersome nor over-expensive, the effects involved were highly
entertaining, and the literature encouraged the duplication of experi-
ments.
9
Hale's major intellectual spur was probably the Cartesian explanation.
Descartes attributed the magnet's power, which was an obvious problem
for his system, to invisible screw-shaped particles passing through special
grooves.
10
There was also a brilliant Hobbesian conjecture that some kind
of vibration was involved, but Hale was as always reluctant to give any
space to the atheist's ideas.
11
He concentrated fire on the 'Epicurean or
Cartesian philosophy', which attributed not just magnetism but even
sentience to 'matter and its various modifications'. It had ignored an
'internal active principle', and was open to several practical objections.
12
A
lump of iron wholly surrounded with gold, the densest (and therefore least
porous) of known bodies, was still affected by the magnet's power.
13
Hale
was sure he could propose a less implausible hypothesis.
The property of loadstones that most interested Hale was the way they
could communicate their powers. A magnet had a capacity to 'generate'
another, impressing its north/south axis (Hale called this its 'verticity') on
a previously lifeless stock of iron.
14
Hale set out to discover whether this
generation created what he called a 'specifical form' or only 'a magnetical
quality as fire [infuses] heat into water', whether, in fact, the magnet was a
ferment.
15
The evidence strongly suggested that it was. The magnetic poles
of a given stone could always be reversed, if brought in contact with a
stronger magnet, but they subsequently tended to revert to their previous
state.
16
This showed that the poles were intrinsic, and not a removable
7
Aristotle, De anima, tr. J. A. Smith, Oxford 1931, Book I, Chapter 2; Lambeth 3501, 1.
8
Gilbert, De magnete, tr. Fleury Mottelay pp. 24-6.
9
Mark Ridley, A short treatise of magnetical bodies and motions, 1613, sig. A3.
10
Descartes, Principles, 243. Discussed by Hale, Lambeth 3501, 35-6; 3502, 80-2.
11
Hobbes, The English works of Thomas Hobbes, ed. Molesworth, vol. I, p. 527.
12
Lambeth 3502, 80.
13
Ibid.,
81-2.
14
Lambeth 3501, 32. Hale treats the magnet in the MS volumes Lambeth 3501-3; Lambeth
3503,
a work of edification entitled Magnetismus magnus, was published in 1695.
Lambeth 3501 cannot be earlier than 1672, because it refers (fo. 62) to George Sinclair's
work on coal mines published in that year.
15
Lambeth 3501, 4-5.
16
Lambeth 3502, 18-19.