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 researches. The papers now before
me were objects of daily and nightly study with me eighteen or
nineteen years ago; but even now, though their perusal is but the
last of a series of repetitions, they astonish me. Every
circumstance connected with the subject; every shade of deportment;