These aetherial lines of force stretch out into space on every side of the sun, and in fact form concentric magnetic shells around the sun; which magnetic shells coincide with the equipotential surfaces of the Aether viewed merely from the point of elasticity and density of the medium. We learn by experiment, that these lines are closest together nearest to the magnet, which fact agrees with the statement that Aether is gravitative, and therefore the Aether would be densest nearest the sun. That is, the atoms would be pressed closer together, so that the lines of force of which these atoms are composed ought also to be closer together at the surface of the magnet, which we find by experiment is the case. As the sun is an electro-magnet, therefore, it possesses these magnetic lines of force on all sides, forming a series of magnetic shells. We have now arrived by the aid of Maxwell's theory to a physical conception of the Aether from a magnetic standpoint, which fully agrees with our physical conception of the Aether which was arrived at by purely philosophical reasoning, based on Newton's Rules of Philosophy. Thus we are able to combine into one whole by our conception that Aether is matter, and therefore atomic and gravitative, not only Faraday's Lines of Force, but also Maxwell's physical conception of the same, apart from the solutions given to the other problems of science by the self-same conception, which solutions will be dealt with in their proper order. As further evidence of Maxwell's belief in the physical existence of Faraday's Lines of Force, let me again quote from his paper on "Action at a Distance,"[36] already referred to in Art. 43. He writes: "Its minute parts may have rotatory as well as vibratory motions, and the axes of rotation form those lines of Magnetic Force which extend in unbroken continuity into regions which no eye has seen.... These lines must _not be regarded as mere mathematical abstractions_. They are the directions in which the medium is exerting tension like that of a rope, or rather like that of our own muscles." [Footnote 34: _Exp. Res._] [Footnote 35: _Magnetism and Electricity._] [Footnote 36: _Collected Works_, by Niven.] ART. 90. _Terrestrial Magnetism._--We have already seen that the earth is a magnet, and like any other magnet will therefore possess its magnetic field with its magnetic lines of force. The earth's magnetic field is co-existent and co-equal with its electric field (Art. 80), and that is co-existent with the earth's aetherial atmosphere which is held bound to the planet by the force of gravity.