We find the electro-magnetic Aether constantly circulating round the planetary magnets, with the result that not only will the current continue to revolve around the planet, but the planet will continue to revolve upon its axis as it revolves round the current. In fact we get in space an example of perpetual motion. We know that the rotation of the earth on its axis has been in existence for several thousand years, and therefore we have a right to assume that it revolved on its axis through the untold ages of past geological times as revealed by the strata, and rocks of pre-historic ages. Thus the motion must have continued, so far as the earth is concerned, at least 100,000,000 years, accepting that period as the age of the earth, but no physical reason so far as I know has ever been assigned for such continued rotation. If, therefore, it be true that the joint action of a current and a magnet is a rotatory one, then, seeing that in all planetary and stellar space we have both these conditions of matter, that is, the electro-magnetic aetherial current, constantly circulating round an electro-magnet, we have, in space, the conditions by which perpetual rotation may be maintained. We have therefore presented to us in that joint action, the true cause of the continued rotation of the earth on its axis, and therefore of all the planets on their axes, together with the sun on its axis; and, if we carry the principle into the stellar world, we can philosophically come to the conclusion that the same conditions prevail there that prevail in the solar system, with the result that we have now a physical cause which fully satisfies all Rules of Philosophy to account for certain phenomena which up to the present have never yet been accounted for from the physical standpoint. Thus in solving the problem of the earth's rotation on its axis, we find greater confirmation in the view presented in a previous article as to the circulating motion of the electro-magnetic Aether around any and every body in space. 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 Ampère.