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Faraday as a Discoverer

Chapter 12
Magnetism of flame and gases--atmospheric magnetism
When an experimental result was obtained by Faraday it was instantly enlarged by his
imagination. I am acquainted with no mind whose power and suddenness of expansion at
the touch of new physical truth could be ranked with his. Sometimes I have compared the
action of his experiments on his mind to that of highly combustible matter thrown into a
furnace; every fresh entry of fact was accompanied by the immediate development of
light and heat. The light, which was intellectual, enabled him to see far beyond the
boundaries of the fact itself, and the heat, which was emotional, urged him to the
conquest of this newly-revealed domain. But though the force of his imagination was
enormous, he bridled it like a mighty rider, and never permitted his intellect to be
In virtue of the expansive power which his vivid imagination conferred upon him, he rose
from the smallest beginnings to the grandest ends. Having heard from Zantedeschi that
Bancalari had established the magnetism of flame, he repeated the experiments and
augmented the results. He passed from flames to gases, examining and revealing their
magnetic and diamagnetic powers; and then he suddenly rose from his bubbles of oxygen
and nitrogen to the atmospheric envelope of the earth itself, and its relations to the great
question of terrestrial magnetism. The rapidity with which these ever-augmenting
thoughts assumed the form of experiments is unparalleled. His power in this respect is
often best illustrated by his minor investigations, and, perhaps, by none more strikingly
than by his paper 'On the Diamagnetic Condition of Flame and Gases,' published as a
letter to Mr. Richard Taylor, in the 'Philosophical Magazine' for December, 1847. After
verifying, varying, and expanding the results of Bancalari, he submitted to examination
heated air-currents, produced by platinum spirals placed in the magnetic field, and raised
to incandescence by electricity. He then examined the magnetic deportment of gases
generally. Almost all of these gases are invisible; but he must, nevertheless, track them in
their unseen courses. He could not effect this by mingling smoke with his gases, for the
action of his magnet upon the smoke would have troubled his conclusions. He, therefore,
'caught' his gases in tubes, carried them out of the magnetic field, and made them reveal
themselves at a distance from the magnet.
Immersing one gas in another, he determined their differential action; results of the
utmost beauty being thus arrived at. Perhaps the most important are those obtained with
atmospheric air and its two constituents. Oxygen, in various media, was strongly attracted
by the magnet; in coal-gas, for example, it was powerfully magnetic, whereas nitrogen
was diamagnetic. Some of the effects obtained with oxygen in coal-gas were strikingly
beautiful. When the fumes of chloride of ammonium (a diamagnetic substance) were
mingled with the oxygen, the cloud of chloride behaved in a most singular manner,-- 'The
attraction of iron filings,' says Faraday, 'to a magnetic pole is not more striking than the
appearance presented by the oxygen under these circumstances.'