Chapter 11.

Discovery of diamagnetism--researches on magne-crystallic action.

Faraday's next great step in discovery was announced in a memoir on
the 'Magnetic Condition of all matter,' communicated to the Royal
Society on December 18, 1845. One great source of his success was
the employment of extraordinary power. As already stated, he never
accepted a negative answer to an experiment until he had brought to
bear upon it all the force at his command. He had over and over
again tried steel magnets and ordinary electro-magnets on various
substances, but without detecting anything different from the
ordinary attraction exhibited by a few of them. Stronger coercion,
however, developed a new action. Before the pole of an electro-magnet,
he suspended a fragment of his famous heavy glass; and observed that
when the magnet was powerfully excited the glass fairly retreated
from the pole. It was a clear case of magnetic repulsion. He then
suspended a bar of the glass between two poles; the bar retreated
when the poles were excited, and set its length equatorially or at
right angles to the line joining them. When an ordinary magnetic
body was similarly suspended, it always set axially, that is, from
pole to pole.

Faraday called those bodies which were repelled by the poles of a
magnet, diamagnetic bodies; using this term in a sense different
from that in which he employed it in his memoir on the magnetization
of light. The term magnetic he reserved for bodies which exhibited
the ordinary attraction. He afterwards employed the term magnetic