. We shall deal again with the relation of a current and a
magnet, when we come to the physical explanation of Kepler's Laws.

ART. 93. _Vortex Motion._--From Art. 91 we have seen that the
electro-magnetic Aether possesses a circulating or rotatory motion
around each central body, and because of this rotatory motion, the body
is at once converted into a magnet. We have also seen that Professor
Challis believed in the circulatory or rotatory motion of the Aether, as
also did Ampere.

Thus we are led back by scientific experiment and philosophical
reasoning to the conception of vortex motion with which the world was
familiar in the days of Kepler, Descartes, Huyghens and Bernoulli. There
is this difference, however, that whereas the vortex motion of those
philosophers was to displace and do away with Gravitation, the
circulatory or rotatory Aether suggested by electro-magnetic phenomena
is to supplement, confirm and establish more firmly than ever the true
powers and laws of Gravitation Attraction.

Before passing, it will be as well to briefly glance at the conception
of vortex motion as suggested by Kepler and Descartes and others.
Whewell on this matter in his _Inductive Sciences_ states that "Kepler
assumed that a certain force or virtue resided in the sun by which all
bodies within his influence were carried round him. He illustrated the
nature of the force in various ways, comparing it to light, and to the
magnetic power which it resembles in the circumstances of operating at a
distance, and also of exercising a feebler influence as the distance
increases." "Another image to which he referred suggested a much more
conceivable kind of mechanical action by which the celestial motions
might be produced, viz. a current of fluid matter circulating round the
sun, and carrying the planets with it like a boat in a stream." Whewell
adds: "A Vortex fluid constantly whirling round the sun, kept in this
whirling motion by the sun itself, and carrying the planets round the
sun by its revolution, as a whirlpool carries straws, could be readily
understood, and though it appears to have been held by Kepler that this
current and Vortex were immaterial, he ascribes to it the power of
overcoming the inertia of bodies, and of putting them and keeping them
in motion."

Now, as we have seen, the electro-magnetic Aether is not immaterial but
material, as it is matter possessing mass and inertia, the same as any
other matter, as Tynd