The main object of the author in Chapters VI., VII., and VIII., is to prove beyond the possibility of contradiction, from the phenomena of heat, light, and electricity, the existence of _two_ forces in the solar system; and by so doing, to bring our philosophy of the aether medium, and all gravitational phenomena, into harmony with all observation and experiments, which at present is not the case. In seeking to do this he found that the new theory of the aether harmonized with views given, by Faraday and Clerk Maxwell in relation to electric and magnetic phenomena, and by the new theory Maxwell's hypothesis of "Physical Lines of Force" receives a definite and physical basis. In Chapter X. the author endeavours to show what the Electro-Kinetic energy is, which term is used by Clerk Maxwell, the term being brought for the first time into harmony with our experience. The Electro-Magnetic Theory of Light also receives fresh light from the new theory of an atomic and gravitating aether. In the succeeding chapters the theory is applied to Newton's Laws of Motion and Kepler's Laws, and is found to harmonize with all the results given by these laws. Such a result is a distinct advance on the application of a frictionless aether to solar and stellar phenomena, as it is impossible for Kepler's Laws to be reconciled in any way with our present theory of the aether. In the concluding chapter on the unity of the universe, certain views are suggested as to the ultimate constitution of all matter, upon an aetherial basis, which hypothesis practically resolves itself into an electric basis for all matter. It is suggested that aether and electricity are one and the same medium, both being a form of matter, and both possessing exactly the same properties, viz. atomicity, weight, density, elasticity, inertia, and compressibility. This view of matter harmonizes with the most "Modern Views of Matter" as suggested by Sir Oliver Lodge in his Romanes Lecture 1903. The author has accepted Newton's way of spelling "_aether_" as given in his work on _Optics_, and has given "_aetherial_" the same suffix as "material," in order to differentiate the word from "ethereal," which is too metaphysical a term for a material medium. _Nottingham_, _Sept._ 1903. CONTENTS CHAPTER I PHILOSOPHY OF GRAVITATION