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33. If electricity, and therefore magnetism, consist also of 
vibratory motion (an assumption which the obvious interchange 
of the former with other forms of energy necessitates), then the 
probable form of electric and magnetic wave-motion becomes 
an interesting subject of inquiry. It must be observed that 
both electricity and magnetism possess a dual character not 
common to other forms of energy ; there is positive and negative 
electricity, austral and boreal magnetism, but there is no 
analogous a and b condition in light or heat. Now, is there 
any conceivable kind of wave-motion that would present this 
duality of character? Undoubtedly there is — namely, a helical 
wave, in which the motion of each disturbed particle is in a 
circle, the plane of which is perpendicular to the direction of 
the wave. If a helix be called positive when it turns from 
left to right, and negative when it turns the contrary way, from 
right to left, then a progressive motion in the same helix will 
appear positive or negative, according to the end at which it is 
viewed ; also, opposite motions in the same helix may be con- 
ceived to interfere, and to give rise to repulsion, while opposite 
motions in opposite helices would progress without interference 
— like tw r o series of waves on the surface of the water crossing 
each other— and this may, perhaps, be the source of electrical 
attraction. 
34. It has recently been stated that no physicist of note has 
suggested the nature of the motion which constitutes electricity 
and magnetism. That may be so, but it is a fact that some 
years have elapsed since the above suggestion was first made by 
the writer : it has also been made by some others. 
35. The intimate relation- — it may be said the identity — -of 
electricity and magnetism may be shown by means of De la 
Rive's floating battery, consisting of a small voltaic element, 
floating in a vessel of water, the electrodes of which are 
connected with the ends of a small cylindrical coil of insulated 
copper wire resting horizontally on the element. This coil 
manifests all the properties of a floating magnetic needle, 
taking its position in the magnetic meridian, and one end being 
attracted, and the other repelled, by either of the poles of a 
bar-magnet. Since magnetic effects are ordinarily exhibited 
by steel or iron, it might be supposed by some that this metal 
is essential to the development of magnetic energy ; it is, 
however, merely the ordinary and most susceptible vehicle of 
magnetism. Since magnetic energy is manifested in a direction 
at right angles to the electric current that produces it, the 
dynamic difficulty of resolving one helical wave into another 
at right angles to the former must not be lost sight of, but it is 
probably not insuperable. There is, however, some valid 
