of this Institution, the most complete antithesis was established
between magnetism and diamagnetism. This antithesis embraced the
quality of polarity,--the theory of reversed polarity, first
propounded by Faraday, being proved to be true. The discussion of
the question was very brisk. On the Continent Professor Wilhelm
Weber was the ablest and most successful supporter of the doctrine
of diamagnetic polarity; and it was with an apparatus, devised by
him and constructed under his own superintendence, by Leyser of
Leipzig, that the last demands of the opponents of diamagnetic
polarity were satisfied. The establishment of this point was
absolutely necessary to the explanation of magne-crystallic action.

With that admirable instinct which always guided him, Faraday had
seen that it was possible, if not probable, that the diamagnetic
force acts with different degrees of intensity in different
directions, through the mass of a crystal. In his studies on
electricity, he had sought an experimental reply to the question
whether crystalline bodies had not different specific inductive
capacities in different directions, but he failed to establish any
difference of the kind. His first attempt to establish differences
of diamagnetic action in different directions through bismuth, was
also a failure; but he must have felt this to be a point of cardinal
importance, for he returned to the subject in 1850, and proved that
bismuth was repelled with different degrees of force in different
directions. It seemed as if the crystal were compounded of two
diamagnetic bodies of different strengths, the substance being more
strongly repelled across the magne-crystallic axis than along it.
The same result was obtained independently, and extended to various
other bodies, magnetic as well as diamagnetic, and also to
compressed substances, a little subsequently by myself.