in part, carbonate of iron for carbonate of lime, thus changing the
magnetic but not the optical character of the crystal, to cause the
axis to be attracted. That the deportment of magnetic crystals is
exactly antithetical to that of diamagnetic crystals isomorphous
with the magnetic ones, was proved to be a general law of action.
In all cases, the line which in a diamagnetic crystal set equatorially,
always set itself in an isomorphous magnetic crystal axially.
By mechanical compression other bodies were also made to imitate the
Iceland spar.

These and numerous other results bearing upon the question were
published at the time in the 'Philosophical Magazine' and in
'Poggendorff's Annalen'; and the investigation of diamagnetism and
magne-crystallic action was subsequently continued by me in the
laboratory of Professor Magnus of Berlin. In December, 1851, after
I had quitted Germany, Dr. Bence Jones went to the Prussian capital
to see the celebrated experiments of Du Bois Reymond. Influenced, I
suppose, by what he there heard, he afterwards invited me to give a
Friday evening discourse at the Royal Institution. I consented, not
without fear and trembling. For the Royal Institution was to me a
kind of dragon's den, where tact and strength would be necessary to
save me from destruction. On February 11, 1853, the discourse was
given, and it ended happily. I allude to these things, that I may
mention that, though my aim and object in that lecture was to
subvert the notions both of Faraday and Plucker, and to establish in
opposition to their views what I regarded as the truth, it was very
far from producing in Faraday either enmity or anger. At the
conclusion of the lecture, he quitted his accustomed seat, crossed
the theatre to the corner into which I had shrunk, shook me by the
hand, and brought me back to the table. Once more, subsequently,