ed away as light-waves.

[Illustration: FIG. 12.]

[Illustration: FIG. 13.]

A puzzling electrical phenomenon has been what has been called its
duality-states, which are spoken of as positive and negative. Thus, we
speak of the positive plate of a battery and the negative pole of a
dynamo; and another troublesome condition to idealize has been, how it
could be that, in an electric circuit, there could be as much energy at
the most remote part as at the source. But, if one will take a limp
rope, 8 or 10 feet long, tie its ends together, and then begin to twist
it at any point, he will see the twist move in a right-handed spiral on
the one hand, and in a left-handed spiral on the other, and each may be
traced quite round the circuit; so there will be as much twist, as much
motion, and as much energy in one part of the rope as in any other; and
if one chooses to call the right-handed twist positive, and the
left-handed twist negative, he will have the mechanical phenomenon of
energy-distribution and the terminology, analogous to what they are in
an electric conductor. (Fig. 13.) Are the cases more dissimilar than the
mechanical analogy would make them seem to be?

Are there any phenomena which imply that rotation is going on in an
electric conductor? There are. An electric arc, which is a current in
the air, and is, therefore, less constrained than it is in a conductor,
rotates. Especially marked is this when in front of the pole of a
magnet; but the rotation may be noticed in an ordinary arc by looking at
it with a stroboscope disk, rotated so as to make the light to the eye
intermittent at the rate of four or five hundred per second. A ray of
plane polarized light, parallel with a wire conveying a current, has its
plane of vibration twisted to the right or left, as the current goes
one way or the other through the wire, and to a degree that depends upon
the distance it travels; not only so, but if the ray be sent, by
reflection, back through the same field, it is twisted as much more--a
phenomenon which convinces one that rotation is going on in the space
through which the ray travels. If the ether through which the ray be
sent were simply warped or in some static stress, the ray, after
reflection, would be brought back to its original plane, which is not
the case. This rotation in the ether is produced by what is going on in
the wire. The ether waves called light are interpreted to imply that
molecules originate the