applied to Electric Currents. 345 
ance to its motion. We may now recapitulate the assumptions 
we have made, and the results we have obtained. 
(1) Magneto-electric phenomena are due to the existence of 
matter under certain conditions of motion or of pressure in every 
part of the magnetic field, and not to direct action at a distance 
between the magnets or currents. The substance producing 
these effects may be a certain part of ordinary matter, or it may 
be an ether associated with matter. Its density is greatest in 
iron, and least in diamagnetic substances; but it must be in all 
cases, except that of iron, very rare, since no other substance has 
a large ratio of magnetic capacity to what we call a vacuum. 
(2): The condition of any part of the field, through which limes 
of magnetic force pass, is one of unequal pressure in different 
directions, the direction of the lines of force being that of least 
pressure, so that the lines of force may be considered lines of 
tension. 
(3) This inequality of pressure is produced by the existence 
in the medium of vortices or eddies, having thei axes in the 
direction of the lines of force, and having their direction of rota- 
tion determined by that of the lines of force. 
We have supposed that the direction was that of a watch to a 
spectator looking from south to north. We might with equal 
_ propriety have chosen the reverse direction, as far as known facts 
are concerned, by supposing resinous electricityinstead of vitreous 
to be positive. The effect of these vortices depends on their 
density, and on their velocity at the circumference, and is inde- 
pendent of their diameter. The density must be proportional to 
the capacity of the substance for magnetic induction, that of the 
vortices in air beg 1. The velocity must be very great, in 
order to produce so powerful effects in so rare a medium. 
The size of the vortices 1s indeterminate, but is probably very 
small as compared with that of a complete molecule of ordinary 
matter*. ’ 
(4) The vortices are separated: from each other by a single 
layer of round particles, so that a system of cells 1s formed, the 
partitions being these layers of particles, and the substance of 
each cell being capable of rotating as a vortex. 
(5) The particles forming the layer are in rolling contact with 
both the vortices which they separate, but do not rub against 
each other. They are perfectly free to roll between the vortices 
* The angular momentum of the system, of vortices depends on their 
average diameter; so that if the diameter were sensible, we might expect 
that a magnet would behave as if it contamed a revolving body within it, 
and that the existence of this rotation might be detected by experiments on 
the free rotation of a magnet. I have made experiments to investigate this 
question, but have not yet fully tried the apparatus. 
