and is distinctly seen only with the aid of a telescope. The Galaxy sweeps throughout the Heaven, and is brilliantly visible to the naked eye. But it interests man chiefly, although less immediately, on account of its being his home; the home of the Earth on which he exists; the home of the Sun about which this Earth revolves; the home of that “system” of orbs of which the Sun is the centre and primary — the Earth one of seventeen secondaries, or planets — the Moon one of seventeen tertiaries, or satellites. The Galaxy, let me repeat, is but one of the clusters which I have been describing; but one of the miscalled “nebulae” revealed to us — by the telescope alone, sometimes — as faint hazy spots in various quarters of the sky. We have no reason to suppose the Milky Way really more extensive than the least of these “nebulae.” Its vast superiority in size is but an apparent superiority arising from our position in regard to it — that is to say, from our position in its midst. However strange the assertion may at first appear to those unversed in Astronomy, still the astronomer himself has no hesitation in asserting that we are in the midst of that inconceivable host of stars — of suns — of systems — which constitute the Galaxy. Moreover, not only have we — not only has our Sun a right to claim the Galaxy as its own especial cluster, but, with slight reservation, it may be said that all the distinctly visible stars of the firmament, all the stars visible to the naked eye, have equally a right to claim it as their own.
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 eccentrically — 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 thickness, 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 phenomena 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 “nebulae” — 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 of Stars. 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 phenomenon 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 “nebulae” which, on casting our eyes from the Universal belt, we perceive at all points of the firmament — so, I say, are these scattered “nebulae” to be understood as only perspectively scattered, and as but a portion 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, a 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.
When speaking of the vulgar propensity to regard all bodies on the Earth as tending merely to the Earth’s centre, I observed that, “with certain exceptions to be specified hereafter, every body on the Earth tended not only to the Earth’s centre, but in every conceivable direction besides.”16 The “exceptions” refer to those frequent gaps in the Heavens, where our utmost scrutiny can detect not only no stellar bodies, but no indications of their existence; where yawning chasms, blacker than Erebus, seem to afford us glimpses, through the boundary walls of the Universe of Stars, into the illimitable Universe of Vacancy, beyond. Now, as any body, existing on the Earth, chances to pass, either through its own movement or the Earth’s, into a line with any one of these voids, or cosmical abysses, it clearly is no longer attractedin the direction of that void, and for the moment, consequently, is “heavier” than at any period, either after or before. Independently of the consideration of these voids, however, and looking only at the generally unequable distribution of the stars, we see that the absolute tendency of bodies on the Earth to the Earth’s centre, is in a state of perpetual variation.
We comprehend, then, the insulation of our Universe. We perceive the isolation of that — of all that which we grasp with the senses. We know that there exists one cluster of clusters — a collection around which, on all sides, extend the immeasurable wildernesses of a Space to all human perception untenanted. But because upon the confines of this Universe of Stars we are compelled to pause, through want of farther evidence from the senses, is it right to conclude that, in fact, there is no material point beyond that which we have thus been permitted to attain? Have we, or have we not, an analogical right to the inference that this perceptible Universe; that this cluster of clusters, is but one of a series of clusters of clusters, the rest of which are invisible through distance — through the diffusion of their light being so excessive, ere it reaches us, as not to produce upon our retinae a light-impression — or from there being no such emanation as light at all, in those unspeakably distant worlds — or, lastly, from the mere interval being so vast that the electric tidings of their presence in Space, have
