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 here all his efforts to produce any sensible action upon
the polarized beam were ineffectual. He then passed from magnets to
currents, enclosing bars of heavy glass, and tubes containing liquids
and aqueous solutions within an electro-magnetic helix. A current sent
through the helix caused the plane of polarization to rotate, and always
in the direction of the current. The rotation was reversed when the
current was reversed. In the case of magnets, he observed a gradual,
though quick, ascent of the transmitted beam from a state of darkness
to its maximum brilliancy, when the magnet was excited. In the case of
currents, the beam attained at once its maximum. This he showed to be
due to the time required by the iron of the electro-magnet to assume its
full magnetic power, which time vanishes when a current, without iron,
is employed. 'In this experiment,' he says, 'we may, I think, justly
say that a ray of light is electrified, and the electric forces
illuminated.' In the helix, as with the magnets, he submitted air to
magnetic influence 'care