At the meeting of the New York Academy of Sciences February 17th, the
article in the March number of _Harper's Magazine_, entitled "Gary's
Magnetic Motor," was incidentally alluded to, and Prof. C. A. Seeley
made the following remarks: The article claims that Mr. Gary has made
a discovery of a neutral line or surface, at which the polarity of an
induced magnet, while moving in the field of the inducing pole, is
changed. The alleged discovery appears to be an exaggerated statement
of some curious facts, which, although not new, are not commonly
recognized. If a bar of iron be brought up, end on, near a magnetic
pole, the bar becomes an induced magnet, but an induced magnet quite
different from what our elementary treatises seem to predict. On the
first scrutiny it is a magnet without a neutral point, and only one
kind of magnetism--namely, that of the inducing pole. Moreover, the
single pole is pretty evenly distributed over the whole surface, so
that if iron filings be sprinkled on the bar they will be attracted at
all points and completely cover it. Now, if while the bar is covered
by filings it be moved away from the inducing pole, the filings will
gradually and progressively fall, beginning at the end nearest the
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, _à 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.
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