136
DISTRIBUTION OF ELECTRICITY ON MOVING CONDUCTORS III
the differences of potential even for moderate velocities are
of the order of the inducing differences. Induction machines
without metallic rubbers are based on this principle. The
theoretically simplest of such machines consists of a cylinder
rotating under the influence of a constant force. How far,
however, the explanation here indicated is a complete one
must for the present remain a moot question.