by the act of polarization, performed here by Faraday, all
oscillations but those parallel to a certain plane are eliminated.
When the plane of vibration of the polarizer coincides with that of
the analyzer, a portion of the beam passes through both; but when
these two planes are at right angles to each other, the beam is
extinguished. If by any means, while the polarizer and analyzer
remain thus crossed, the plane of vibration of the polarized beam
between them could be changed, then the light would be, in part at
least, transmitted. In Faraday's experiment this was accomplished.
His magnet turned the plane of polarization of the beam through a
certain angle, and thus enabled it to get through the analyzer;
so that 'the magnetization of light and the illumination of the
magnetic lines of force' becomes, when expressed in the language of
modern theory, the rotation of the plane of polarization.

To him, as to all true philosophers, the main value of a fact was
its position and suggestiveness in the general sequence of
scientific truth. Hence, having established the existence of a
phenomenon, his habit was to look at it from all possible points of
view, and to develop its relationship to other phenomena. He proved
that the direction of the rotation depends upon the polarity of his
magnet; being reversed when the magnetic poles are reversed.
He showed that when a polarized ray passed through his heavy glass
in a direction parallel to the magnetic lines of force, the rotation
is a maximum, and that when the direction of the ray is at right
angles to the lines of force, there is no rotation at all. He also
proved that the amount of the rotation is proportional to the length
of the diamagnetic through which the ray passes. He operated with
liquids and solutions. Of aqueous solutions he tried 150 and more,
and found the power in all of them. He then examined gases; but