Faraday as a Discoverer HTML version

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 to cover the
whole phenomena of attraction and repulsion, and used the word paramagnetic to
designate such magnetic action as is exhibited by iron.
Isolated observations by Brugmanns, Becquerel, Le Baillif, Saigy, and Seebeck had
indicated the existence of a repulsive force exercised by the magnet on two or three
substances; but these observations, which were unknown to Faraday, had been permitted
to remain without extension or examination. Having laid hold of the fact of repulsion,
Faraday immediately expanded and multiplied it. He subjected bodies of the most varied
qualities to the action of his magnet:--mineral salts, acids, alkalis, ethers, alcohols,
aqueous solutions, glass, phosphorus, resins, oils, essences, vegetable and animal tissues,
and found them all amenable to magnetic influence. No known solid or liquid proved
insensible to the magnetic power when developed in sufficient strength. All the tissues of
the human body, the blood--though it contains iron-- included, were proved to be
diamagnetic. So that if you could suspend a man between the poles of a magnet, his
extremities would retreat from the poles until his length became equatorial.
Soon after he had commenced his researches on diamagnetism, Faraday noticed a
remarkable phenomenon which first crossed my own path in the following way: In the
year 1849, while working in the cabinet of my friend, Professor Knoblauch, of Marburg, I
suspended a small copper coin between the poles of an electro-magnet. On exciting the
magnet, the coin moved towards the poles and then suddenly stopped, as if it had struck
against a cushion. On breaking the circuit, the coin was repelled, the revulsion being so