If, with a telescope of high space-penetrating power, we carefully inspect the firmament, we shall become aware of _a belt of clusters_—of what we have hitherto called “nebulæ”—a _band_, of varying breadth, stretching from horizon to horizon, at right angles to the general course of the Milky Way. This band is the ultimate _cluster of clusters_. This belt is _The Universe_. Our Galaxy is but one, and perhaps one of the most inconsiderable, of the clusters which go to the constitution of this ultimate, Universal _belt_ or _band_. The appearance of this cluster of clusters, to our eyes, _as_ a belt or band, is altogether a perspective phænomenon of the same character as that which causes us to behold our own individual and roughly-spherical cluster, the Galaxy, under guise also of a belt, traversing the Heavens at right angles to the Universal one. The shape of the all-inclusive cluster is, of course _generally_, that of each individual cluster which it includes. Just as the scattered stars which, on looking _from_ the Galaxy, we see in the general sky, are, in fact, but a portion of that Galaxy itself, and as closely intermingled with it as any of the telescopic points in what seems the densest portion of its mass—so are the scattered “nebulæ” which, on casting our eyes _from_ the Universal _belt_, we perceive at all points of the firmament—so, I say, are these scattered “nebulæ” to be understood as only perspectively scattered, and as part and parcel of the one supreme and Universal _sphere_. No astronomical fallacy is more untenable, and none has been more pertinaciously adhered to, than that of the absolute _illimitation_ of the Universe of Stars. The reasons for limitation, as I have already assigned them, _à priori_, seem to me unanswerable; but, not to speak of these, _observation_ assures us that there is, in numerous directions around us, certainly, if not in all, a positive limit—or, at the very least, affords us no basis whatever for thinking otherwise. Were the succession of stars endless, then the background of the sky would present us an uniform luminosity, like that displayed by the Galaxy—_since there could be absolutely no point, in all that background, at which would not exist a star._ The only mode, therefore, in which, under such a state of affairs, we could comprehend the _voids_ which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all. That this _may_ be so, who shall venture to deny? I maintain, simply, that we have not even the shadow of a reason for believing that it _is_ so.