A feature common to both these theories rested in the fact, that they supposed that all material bodies which exist in the universe once existed in a nebulous condition, and that they were formed out of this nebulous matter. Further, that this nebulous matter gradually condensed, and as it condensed, a rotational motion was imparted to them, which rotation quickened as the condensation was continued. Then, as the rotation was accelerated, portions were flung off by the centrifugal force, and these portions of nebulous matter gradually condensed, forming the various planets of the system. As these condensed, they, in their turn, parted with some of their nebulous matter through the repulsive energy of the centrifugal force, and these secondary parts gave origin to the various satellites that exist round the planets. Now, while the general principle involved in the nebular hypothesis is true, yet the conception according to Laplace is not verified by fact, as we learn that Uranus and Neptune are still in a state of self-luminosity, while their density is the smallest of all the planets. From this we should infer that the two outermost planets are the youngest planets of our solar system, but according to Laplace's theory, they ought to be the oldest, as they would have been flung off first by the parent body as it rotated; and therefore, being flung off first, should be in a more advanced stage of development than any of the inner planets. M. Faye has suggested a remedy for this defect in the theory. He supposes that the nebulous matter out of which the planets were formed, was not flung off by the central body the sun, but that each planet was formed at different centres of condensation within the nebular mass that existed in space. This would, undoubtedly, meet the difficulty already referred to, and solves the problem as to how the various planets were formed at different distances in space. Further, such a solution is in perfect harmony with all the Rules of Philosophy. It is much more simple to conceive of Aether condensing at various points in what originally was the solar nebula, than it is to conceive of Aether condensing and shrinking towards one central point, and yet while condensing and shrinking, portions were flung off into space which would form the planet. A greater objection has to be met, when we come to deal with the origin of all the meteors and minor planets that exist in their numbers in the solar system. In relation to their origin, it is much easier to conceive of portions of the Aether condensing at different centres of condensation, than to suppose that each portion of aetherial matter that originally formed the meteor, or asteroid, was flung off as a separate portion from the central body.