o the opinion that the action of a magnet upon bismuth is a
true and absolute repulsion, and not merely the result of differential
attraction. And then he clearly states a theoretic view sufficient to
account for the phenomena. 'Theoretically,' he says, 'an explanation of
the movements of the diamagnetic bodies, and all the dynamic phenomena
consequent upon the action of magnets upon them, might be offered in the
supposition that magnetic induction caused in them a contrary state to
that which it produced in ordinary matter.' That is to say, while in
ordinary magnetic influence the exciting pole excites adjacent to itself
the contrary magnetism, in diamagnetic bodies the adjacent magnetism is
the same as that of the exciting pole. This theory of reversed polarity,
however, does not appear to have ever laid deep hold of Faraday's mind;
and his own experiments failed to give any evidence of its truth. He
therefore subsequently abandoned it, and maintained the non-polarity of
the diamagnetic force.

He then entered a new, though related field of inquiry. Having dealt
with the metals and their compounds, and having classified all of
them that came within the range of his observation under the two heads
magnetic and diamagnetic, he began the investigation of the phenomena
presented by crystals when subjected to magnetic power. This action of
crystals had been in part theoretically predicted by Poisson,[2] and
actually discovered by Plucker, whose beautiful results, at the period
which we have now reached, profoundly interested all scientific men.
Faraday had been frequently puzzled by the deportment of bismuth, a
highly crystalline metal. Sometimes elongated masses of the substance
refused to set equatorially, sometimes they set persistently oblique,
and sometimes even, like a magnetic body, from pole to pole.

'The effect,' he says, 'occurs at a single pole; and it is then striking
to observe a long piece of a substance so diamagnetic as bismuth
repelled, and yet at the same moment set round with force, axially, or
end on, as a piece of magnetic substance would do.' The effect perplexed
him; and in his efforts to release himself from this perplexity, no
feature of this new manifestation of force escaped his attention. His
experiments are described in a memoir communicated to the Royal Society
on December 7, 1848.

I have worked long myself at magne-crystallic action, amid all the light
of Faraday's and Plucker's researche