their action.... This strong persuasion,' he adds, 'extended to the
powers of light.' And then he examines the action of magnets upon
light. From conversation with him and Anderson, I should infer that
the labour preceding this discovery was very great. The world knows
little of the toil of the discoverer. It sees the climber jubilant
on the mountain top, but does not know the labour expended in
reaching it. Probably hundreds of experiments had been made on
transparent crystals before he thought of testing his heavy glass.
Here is his own clear and simple description of the result of his
first experiment with this substance:--'A piece of this glass, about
two inches square, and 0.5 of an inch thick, having flat and
polished edges, was placed as a diamagnetic[1] between the poles
(not as yet magnetized by the electric current), so that the
polarized ray should pass through its length; the glass acted as
air, water, or any other transparent substance would do; and if the
eye-piece were previously turned into such a position that the
polarized ray was extinguished, or rather the image produced by it
rendered invisible, then the introduction of the glass made no
alteration in this respect. In this state of circumstances, the
force of the electro-magnet was developed by sending an electric
current through its coils, and immediately the image of the
lamp-flame became visible and continued so as long as the
arrangement continued magnetic. On stopping the electric current,
and so causing the magnetic force to cease, the light instantly
disappeared. These phenomena could be renewed at pleasure, at any
instant of time, and upon any occasion, showing a perfect dependence
of cause and effect.'

In a beam of ordinary light the particles of the luminiferous ether
vibrate in all directions perpendicular to the line of progression;