"I do not know a treatise in which a survey of the Universe using the word in its most comprehensive and only legitimate acceptation is taken at all: and it may be as well here to mention that by the term "Universe," wherever employed without qualification in this essay, I mean to designate the utmost conceivable expanse of space, with all things, spiritual and material, that can be imagined to exist within the compass of that expanse. In speaking of what is ordinarily implied by the expression, "Universe," I shall take a phrase of limitation "the Universe of stars." Why this distinction is considered necessary, will be seen in the sequel."