When we come to deal with the earth as a magnet more directly, we shall see that all the variations of terrestrial magnetism may be satisfactorily explained by the fact that the sun is, as we have indicated in this article, an electro-magnet, possessing its magnetic field with its lines of force, and therefore able to give rise to all the phenomena incidental to and associated with any ordinary magnet. ART. 89. _Aether and Faraday's Lines of Force._--We have now to face the question of the physical character of the Lines of Force conceived by Faraday. We have seen in Fig. 18 illustration of these lines of force, which are manifested by the iron filings in the neighbourhood of a magnet, and the question suggests itself to the mind, as to what is the relation of the Aether to those lines of force? Does the Aether play any part in their existence, and if so what? Faraday was of the opinion that the Aether did play some part in the existence of the lines, and that they were no mere hypothetical lines, but were caused by the actual physical state or condition of the aetherial medium, which existed around every magnet and every electrified body. On this point he says, Art. 3263:[34] "To acknowledge the action in curved lines seems to me to imply at once that the lines have a physical existence. It may be the vibration of the hypothetical Aether, or a state of tension of that Aether equivalent to either a dynamic or static condition." Par. 3277: "I conceive that when a magnet is in free space, there is such a medium, magnetically speaking, around it. That a vacuum has its own magnetic relations of attractions and repulsions is manifest from former experimental results (2787). What that surrounding magnetic medium deprived of all material substance may be, I cannot tell, perhaps the Aether." It was, however, left for Clerk Maxwell to develop the idea as to their physical character, and this he did in his paper on "Physical Lines of Force," _Phil. Mag._, 1861. He had previously written a paper on "Faraday's Lines of Force," delivered to the Cambridge Phil. Society in 1855 and 1856, but his more matured conception of Faraday's Lines of Force was given in the later article.