Is space, then, eternal, and is this constant round of energies to be eternal? If one is eternal, so is the other, and surely nothing can be more eternal than space, and we cannot conceive of any other space than this space. Out of it came all created things, and so long as the orbs rotate without retardation, so long will these interchanges go on without impairment, and that they do so rotate is the necessary corollary of the fact that they ever began to rotate. If rotation, on the contrary, was imparted by special creative power, then the same power established the laws by which they rotate, and took cognizance of resistance as well. Whatever the impulse was, it still remains; whatever caused the rotation to begin maintains it; if the cause is eternal the rotation may be eternal; and, in any case, its period must be measured by cycles of æons, to which the allotted lifetime of a dying sun--a few million years, perhaps--is but as the sunburst of a morning-glory flower to the hoary age of a mighty planet. Compared with the popular view of the sun's life-period, we may formulate the terms of an equation in which the sun's mass, compared with the realms of infinite space, is as the sun's lifetime--on a basis of contraction of his volume--to the lifetime which actually is to be. As one of the terms is practically infinite, so must be the answer to the problem. Professor Stewart says, "We cannot help believing that there is a material medium of some kind between the sun and the earth; indeed, the undulatory theory of light requires this belief." It has already been shown that the transmission of electricity also requires it, but that there must be a medium quite different from the undulatory ether. Professor Proctor ("Mysteries of Time and Space") says, "We may admit the possibility that the aqueous vapor and carbon compounds are present in stellar or interplanetary space." Again he says, "Assuming, as we well may, that space is really occupied by attenuated vapors." The same writer says further, "To this end all thoughtful study of the mechanism seems to tend (associating, perhaps, our visible universe with others, permeating it as the ether of space permeates the densest solids, and in turn with others so permeated by it); there may be that constant interchange, that perpetual harmony, of which Goethe sung: 'Balanced worlds from change defending, While everywhere diffused is harmony unending.'"