e
inducing pole and continuing to some point near the middle of the bar;
the filings at the remote end will generally be held permanently. When
the bar is carried beyond the field of the inducing pole it is simply
a weak magnet of ordinary properties--_i. e._, of two poles and a
neutral point between them.

A plausible and simple explanation of this case is that the inducing
pole holds or binds the induced magnetism of opposite name, so that it
has no external influence; the two magnetisms are related to each
other as are the positive and negative electricities of the Leyden
jar. Let the inducing pole be N.; the S. of the bar will be attracted
by it and bound, while the N. of the bar becomes abnormally free and
active. On moving the bar from the pole the bound magnetism is
released and a part becomes residual magnetism. Now when the residual
balances the free magnetism which is of opposite name, we are on
Gary's neutral line. In a restricted sense there is a change of
polarity over the half of the bar contiguous to the inducing pole; on
the other half there is no change of pole in any sense. Experiment
with a shingle nail in the place of the filings, _a la_ Gary,
bring the nail to the induced bound pole, and it may be held, except
at the neutral line. Now if one will read the magazine article with
such ideas as these he will feel pretty sure that the writer of it has
used words recklessly, that Gary has not made an original discovery,
and that the "neutral" line, whatever it be, has only an imagined
relation to the "principle" of the motor.

The Gary Motor as a perpetual motion scheme, of course, is not worthy
of serious notice from a society devoted to science. It has no
noteworthy novelty of construction or conception. Mr. Gary is
afflicted with the very old delusion of the cut-off or shield of
magnetism, which is to cost less than what comes from it. His cut-off
is a sheet of iron, which we know acts simply as an armature.

* * * * *

A NEW PHENOMENON IN STATICAL ELECTRICITY.

M. E. Duter, in a paper read before the French Academy in December,
showed that when a Leyden jar is charged with either positive or
negative electricity its internal volume increases, and that this
effect is a new phenomenon, unexplainable by either a theory of an
increase of temperature or of an electrical pressure. The experiment
was performed by means of a flask-shaped Leyden jar with a long tube