XCVII
CHAPTER XIII.
Magnetism.
411–417.
§ 233. Definition. Natural and artificial magnets.
The two poles. 411. Besides the two ends of a magnet where
attraction is most powerful, there is a line in the middle from
which magnetism is distributed, which is called the neutral line
and which shows no attraction at all.
Remark. Plato and Pythagoras had discovered the magnetical power
or the property in some bodies to attract iron. Magnets attract iron,
even if other bodies are in the middle. (Put iron filings on paper or on
a book and hold the magnet on the other side.)
§ 234. If free motion is given to a magnet, one pole turns
to the north, the other one to the south.
§ 235. Poles of contrary name attract each other, and poles
of the same name repel each other, if the contrary magnetism is
of the same strength they neutralize each other (law of Polarity).
§ 236, Magnetism is inversely as the square of the distance
(cf. sound, light); the strength can be estimated by the oscilla
tions of a magnet, which we have diverted from its normal
direction.
§ 237. Influence of magnets upon magnetic substances.
412. Magnetic bodies are such bodies in which both kinds of
magnetism are present, but check or bind each other thus
producing a neutral state. In magnets the two kinds of
magnetism are separated in each molecule and each produces
a separate effect, hence a magnet broken in the midst gives two
whole ones. 413.
§ 238. Magnetisation by magnets consists in moving the
north-pole of a powerful magnet from the middle of the steel
G
