Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.
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and magnetizing, the other at the instant of passing off and de-
magnetizing.
The magneto-electric machine is heavy according - to its
power; but it is in a box, compact, dry, and neat. Its inten-
Fig. 21. Magneto-Electric Portable Machine complete in its Bos.
sity depends, first, upon the power of the great magnet, whether
single or compound; second, tipon the size of the wire that is
wound around the armature, and also upon the number of its
convolutions ; third, upon the exact nearness of the revolving
armature to the tips of the poles or arms of the great magnet;
fourth, and finally, upon the velocity and regularity with which
the wheel is turned.
In this machine it is easy to arrange a spring cut-off on the
large shaft of the armature so as to strike an alternate cog of
brass and ivory, and thus to effectually intercept one set of
the shocks that make up a one-way current, leaving the other
to pass to the electrodes, as a current made up of fine shocks
or bits of currents, but all in one direction. This can be
demonstrated by showing decomposition of iodide of potassium
or starch only at one pole. Thus we have not only an induction
current with a nominal polo, but here are the positive and nega-
tive poles truly so in effect.
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