XX
ON THE RELATIONS BETWEEN LIGHT AND
ELECTRICITY
A LECTURE DELIVERED AT THE SIXTY-SECOND MEETING OF
THE GERMAN ASSOCIATION FOR THE ADVANCEMENT OF
NATURAL SCIENCE AND MEDICINE IN HEIDELBERG ON
SEPTEMBER 20TH, 1889.
(Published by Emil Strauss in Bonn.)
WHEN one speaks of the relations between light and elec-
tricity, the lay mind at once thinks of the electric light.
With this the present lecture is not concerned. To the mind
of the physicist there occur a series of delicate mutual reactions
between the two agents, such as the rotation of the plane of
polarisation by the current or the alteration of the resistance
of a conductor by the action of light. In these, however,
light and electricity do not directly meet; between the two
there comes an intermediate agent―ponderable matter. With
this group of phenomena again we shall not concern ourselves.
Between the two agents there are yet other relations-rela-
tions in a closer and stricter sense than those already men-
tioned. I am here to support the assertion that light of
every kind is itself an electrical phenomenon the light of
the sun, the light of a candle, the light of a glow-worm.
Take away from the world electricity, and light disappears;
remove from the world the luminiferous ether, and electric
and magnetic actions can no longer traverse space. This is
our assertion. It does not date from to-day or yesterday;
already it has behind it a long history. In this history its