If steam is used instead of human breath, a considerable weight may
be hung from the disc without dislodging it.
The Magic Swingers.--The easily made toy illustrated next is much more
interesting than would appear from the mere picture, as it demonstrates a
very striking physical phenomenon, the transference of energy. If two
pendulums are hung close together from a flexible support and swung, their
movements influence one another in a somewhat remarkable way--the swing of
the one increasing as that of the other dies down, until a certain point is
reached, after which the process is reversed, and the "dying" or "dead"
pendulum commences to come to life again at the expense of the other. This
alternation is repeated over and over again, until all the energy of both
pendulums is exhausted.
[Illustration: FIG. 148.-Magic pendulums.]
To make the experiment more attractive, we substitute for the simplest
possible pendulums--weights at the end of strings--small swings, each
containing a figure sitting or standing on a seat, to the underside of
which is attached a quarter of a pound of lead.
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