Beacon Lights of History, Volume 14: The New Era: A Supplementary Volume, by Recent Writers, as Set Forth in the Preface and Table of ContentsLord, John
Philosophy
Beacon Lights of History, Volume 14: The New Era: A Supplementary Volume, by Recent Writers, as Set Forth in the Preface and Table of Contents
Lord, John
History
In 1778, Brugmans of Leyden noticed that if a piece of bismuth was held
near either pole of a strong magnet, repulsion occurred. Other observers
noticed the same effect in the case of antimony. These facts appear to
have been unknown to Faraday, who, in 1845, by employing powerful
electro-magnets rediscovered them, and in addition showed that
practically all substances possess the power of being attracted or
repelled, when placed between the poles of sufficiently powerful
magnets. By placing slender needles of the substances experimented on
between the poles of powerful horse-shoe magnets, he found that they were
all either attracted like iron, coming to rest with their greatest
length extending between the poles; or, like bismuth, were apparently
repelled by the poles, coming to rest at right angles to the position
assumed by iron. He regarded the first class of substances as attracted,
and the second class as repelled, and called them respectively
paramagnetic and diamagnetic substances. In other words, paramagnetic
substances, like iron, came to rest axially (extending from pole to
pole), and diamagnetic substances, like bismuth, equatorially (extending
transversely between the poles). He reserved the term magnetic
substances to cover the phenomena of both para and dia-magnetism. He
communicated the results of this investigation to the Royal Society in a
paper on the "Magnetic Condition of All Matter," on Dec. 18, 1845.
The properties of paramagnetism and diamagnetism are not possessed by
solids only, but exist also in liquids and gases. When experimenting
with liquids, they were placed in suitable glass vessels, such as watch
crystals, supported on pole pieces properly shaped to receive them.
Under these circumstances paramagnetic liquids, such as salts of iron or
cobalt dissolved in water, underwent curious contortions in shape, the
tendency being to arrange the greater part of their mass in the
direction in which the flux passed; namely, directly between the poles.
Diamagnetic liquids, such as solutions of salts of bismuth and antimony,
in a similar manner, arranged the greater part of their mass in
positions at right angles to this direction, or equatorially.
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