So that the mass of the Aether at Mercury, which is equal to the number of aetherial atoms per unit volume, is greater than the mass at Venus. Thus the impressed force which the aetherial medium at the mean distance of Mercury can exert upon any body in its neighbourhood, is greater than the impressed force which the Aether can exert upon any body at the distance of Venus, because of its decreased mass at that distance. In the same way it can be proved that the impressed force which the electro-magnetic Aether exerts on any body at the distance of Venus, is greater than the impressed force which the Aether exerts upon a body at the mean distance of the Earth. So that at the respective mean distances of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, the electro-magnetic Aether, if in motion, would exert less force at each of the mean distances of these planets exactly proportionate to the decreased mass and decreased velocity of the Aether. Now what is the motion which the Aether possesses, so far as the sun is concerned? because, upon the particular kind of motion which it possesses will depend the direction in which the impressed force will be exerted according to the second law of motion. In Art. 98 we supposed the sun and planets to be stationary in the solar system, each planet being at its respective mean distance, from which it cannot move owing to the equality of the two forces. Now give to the central sun from whence the electro-magnetic Aether waves flow, a rotatory motion on its own axis, which it really possesses, as it rotates on its axis once in every twenty-six days nearly, and this will give to the Aether medium a circular or rotatory motion. This circular or rotatory motion the Aether has already been proved to possess (Art. 91, where we learned that all solar magnets were caused by electro-magnetic aetherial currents constantly circulating round them). So that the Aether will actually possess two motions: 1st, a radial motion due to the Aether waves generated by the sun, which are radiated out into space with the velocity of light; and 2nd, a circular or rotatory motion. This result is in perfect harmony with our hypothesis as to the cause of the electro-magnetism of the sun (Art. 91, where we saw that solar magnetism was due to electric currents circulating round the various planets), and we have proved that the Aether has an electro-magnetic basis; thus the rotatory Aether currents and the rotatory electro-magnetic currents are due to one and the same medium.