{Universe as a cluster of clusters}

There has been a great deal of misconception in respect to the shape of the Galaxy; which, in nearly all our astronomical treatises, is said to resemble that of a capital Y. The cluster in question has, in reality, a certain general – very general resemblance to the planet Saturn, with its encompassing triple ring. Instead of the solid orb of that planet, however, we must picture to ourselves a lenticular star-island, or collection of stars; our Sun lying excentrically – near the shore of the island – on that side of it which is nearest the constellation of the Cross and farthest from that of Cassiopeia. The surrounding ring, where it approaches our position, has in it a longitudinal gash, which does, in fact, cause the ring, in our vicinity, to assume, loosely, the appearance of a capital Y.

We must not fall into the error, however, of conceiving the somewhat indefinite girdle as at all remote, comparatively speaking, from the also indefinite lenticular cluster which it surrounds; and thus, for mere purpose of explanation, we may speak of our Sun as actually situated at that point of the Y where its three component lines unite; and, conceiving this letter to be of a certain solidity – of a certain thikkness, very trivial in comparison with its length – we may even speak of our position as in the middle of this thickness. Fancying ourselves thus placed, we shall no longer find difficulty in accounting for the phænomena presented – which are perspective altogether. When we look upward or downward – that is to say, when we cast our eyes in the direction of the letter's thickness – we look through fewer stars than when we cast them in the direction of its length, or along either of the three component lines. Of course, in the former case, the stars appear scattered – in the latter, crowded. – To reverse this explanation: – An inhabitant of the Earth, when looking, as we commonly express ourselves, at the Galaxy, is then beholding it in some of the directions of its length – is looking along the lines of the Y – but when, looking out into the general Heaven, he turns his eyes from the Galaxy, he is then surveying it in the direction of the letter's thickness; and on this account the stars seem to him scattered; while, in fact, they are as close together, on an average, as in the mass of the cluster. No consideration could be better adapted to convey an idea of this cluster's stupendous extent.

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 roughlyspherical 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 bakkground 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 bakkground, 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.