Through what we know of the propagation of light, we have direct proof that the more remote of the stars have existed, under the forms in which we now see them, for an inconceivable number of years. So far back _at least_, then, as the period when these stars underwent condensation, must have been the epoch at which the ma.s.s-const.i.tutive processes began.

That we may conceive these processes, then, as still going on in the case of certain "nebulae," while in all other cases we find them thoroughly at an end, we are forced into a.s.sumptions for which we have really _no_ basis whatever-we have to thrust in, again, upon the revolting Reason, the blasphemous idea of special interposition-we have to suppose that, in the particular instances of these "nebulae," an unerring G.o.d found it necessary to introduce certain supplementary regulations-certain improvements of the general law-certain retouchings and emendations, in a word, which had the effect of deferring the completion of these individual stars for centuries of centuries beyond the aera during which all the other stellar bodies had time, not only to be fully const.i.tuted, but to grow h.o.a.ry with an unspeakable old age.

Of course, it will be immediately objected that since the light by which we recognize the nebulae now, must be merely that which left their surfaces a vast number of years ago, the processes at present observed, or supposed to be observed, are, in fact, _not_ processes now actually going on, but the phantoms of processes completed long in the Past-just as I maintain all these ma.s.s-const.i.tutive processes _must_ have been.

To this I reply that neither is the now-observed condition of the condensed stars their actual condition, but a condition completed long in the Past; so that my argument drawn from the _relative_ condition of the stars and the "nebulae," is in no manner disturbed. Moreover, those who maintain the existence of nebulae, do _not_ refer the nebulosity to extreme distance; they declare it a real and not merely a perspective nebulosity. That we may conceive, indeed, a nebular ma.s.s as visible at all, we must conceive it as _very near us_ in comparison with the condensed stars brought into view by the modern telescopes. In maintaining the appearances in question, then, to be really nebulous, we maintain their comparative vicinity to our point of view. Thus, their condition, as we see them now, must be referred to an epoch _far less remote_ than that to which we may refer the now-observed condition of at least the majority of the stars.-In a word, should Astronomy ever demonstrate a "nebula," in the sense at present intended, I should consider the Nebular Cosmogony-_not_, indeed, as corroborated by the demonstration-but as thereby irretrievably overthrown.

By way, however, of rendering unto Caesar _no more_ than the things that are Caesar's, let me here remark that the a.s.sumption of the hypothesis which led him to so glorious a result, seems to have been suggested to Laplace in great measure by a misconception-by the very misconception of which we have just been speaking-by the generally prevalent misunderstanding of the character of the nebulae, so mis-named. These he supposed to be, in reality, what their designation implies. The fact is, this great man had, very properly, an inferior faith in his own merely _perceptive_ powers. In respect, therefore, to the actual existence of nebulae-an existence so confidently maintained by his telescopic contemporaries-he depended less upon what he saw than upon what he heard.

It will be seen that the only valid objections to his theory, are those made to its hypothesis _as_ such-to what suggested it-not to what it suggests; to its propositions rather than to its results. His most unwarranted a.s.sumption was that of giving the atoms a movement towards a centre, in the very face of his evident understanding that these atoms, in unlimited succession, extended throughout the Universal s.p.a.ce. I have already shown that, under such circ.u.mstances, there could have occurred no movement at all; and Laplace, consequently, a.s.sumed one on no more philosophical ground than that something of the kind was necessary for the establishment of what he intended to establish.

His original idea seems to have been a compound of the true Epicurean atoms with the false nebulae of his contemporaries; and thus his theory presents us with the singular anomaly of absolute truth deduced, as a mathematical result, from a hybrid datum of ancient imagination intertangled with modern inac.u.men. Laplace's real strength lay, in fact, in an almost miraculous mathematical instinct:-on this he relied; and in no instance did it fail or deceive him:-in the case of the Nebular Cosmogony, it led him, blindfolded, through a labyrinth of Error, into one of the most luminous and stupendous temples of Truth.

Let us now fancy, for the moment, that the ring first thrown off by the Sun-that is to say, the ring whose breaking-up const.i.tuted Neptune-did not, in fact, break up until the throwing-off of the ring out of which Ura.n.u.s arose; that this latter ring, again, remained perfect until the discharge of that out of which sprang Saturn; that this latter, again, remained entire until the discharge of that from which originated Jupiter-and so on. Let us imagine, in a word, that no dissolution occurred among the rings until the final rejection of that which gave birth to Mercury. We thus paint to the eye of the mind a series of coexistent concentric circles; and looking as well at _them_ as at the processes by which, according to Laplace's hypothesis, they were constructed, we perceive at once a very singular a.n.a.logy with the atomic strata and the process of the original irradiation as I have described it. Is it impossible that, on measuring the _forces_, respectively, by which each successive planetary circle was thrown off-that is to say, on measuring the successive excesses of rotation over gravitation which occasioned the successive discharges-we should find the a.n.a.logy in question more decidedly confirmed? _Is it improbable that we should discover these forces to have varied-as in the original radiation-proportionally to the squares of the distances?_

Our solar system, consisting, in chief, of one sun, with sixteen planets certainly, and possibly a few more, revolving about it at various distances, and attended by seventeen moons a.s.suredly, but _very_ probably by several others-is now to be considered as _an example_ of the innumerable agglomerations which proceeded to take place throughout the Universal Sphere of atoms on withdrawal of the Divine Volition. I mean to say that our solar system is to be understood as affording a _generic instance_ of these agglomerations, or, more correctly, of the ulterior conditions at which they arrived. If we keep our attention fixed on the idea of _the utmost possible Relation_ as the Omnipotent design, and on the precautions taken to accomplish it through difference of form, among the original atoms, and particular inequidistance, we shall find it impossible to suppose for a moment that even any two of the incipient agglomerations reached precisely the same result in the end. We shall rather be inclined to think that _no two_ stellar bodies in the Universe-whether suns, planets or moons-are particularly, while _all_ are generally, similar. Still less, then, can we imagine any two _a.s.semblages_ of such bodies-any two "systems"-as having more than a general resemblance.[10] Our telescopes, at this point, thoroughly confirm our deductions. Taking our own solar system, then, as merely a loose or general type of all, we have so far proceeded in our subject as to survey the Universe under the aspect of a spherical s.p.a.ce, throughout which, dispersed with merely general equability, exist a number of but generally similar _systems_.

[10] It is not _impossible_ that some unlooked-for optical improvement may disclose to us, among innumerable varieties of systems, a luminous sun, encircled by luminous and non-luminous rings, within and without and between which, revolve luminous and non-luminous planets, attended by moons having moons-and even these latter again having moons.

Let us now, expanding our conceptions, look upon each of these systems as in itself an atom; which in fact it is, when we consider it as but one of the countless myriads of systems which const.i.tute the Universe.

Regarding all, then, as but colossal atoms, each with the same ineradicable tendency to Unity which characterizes the actual atoms of which it consists-we enter at once upon a new order of aggregations. The smaller systems, in the vicinity of a larger one, would, inevitably, be drawn into still closer vicinity. A thousand would a.s.semble here; a million there-perhaps here, again, even a billion-leaving, thus, immeasurable vacancies in s.p.a.ce. And if now, it be demanded why, in the case of these systems-of these merely t.i.tanic atoms-I speak, simply, of an "a.s.semblage," and not, as in the case of the actual atoms, of a more or less consolidated agglomeration:-if it be asked, for instance, why I do not carry what I suggest to its legitimate conclusion, and describe, at once, these a.s.semblages of system-atoms as rushing to consolidation in spheres-as each becoming condensed into one magnificent sun-my reply is that e????ta ta?ta-I am but pausing, for a moment, on the awful threshold of _the Future_. For the present, calling these a.s.semblages "cl.u.s.ters," we see them in the incipient stages of their consolidation.

Their _absolute_ consolidation is _to come_.

We have now reached a point from which we behold the Universe as a spherical s.p.a.ce, interspersed, _unequably_, with _cl.u.s.ters_. It will be noticed that I here prefer the adverb "unequably" to the phrase "with a merely general equability," employed before. It is evident, in fact, that the equability of distribution will diminish in the ratio of the agglomerative processes-that is to say, as the things distributed diminish in number. Thus the increase of _in_-equability-an increase which must continue until, sooner or later, an epoch will arrive at which the largest agglomeration will absorb all the others-should be viewed as, simply, a corroborative indication of the _tendency to One_.

And here, at length, it seems proper to inquire whether the ascertained _facts_ of Astronomy confirm the general arrangement which I have thus, deductively, a.s.signed to the Heavens. Thoroughly, they _do_. Telescopic observation, guided by the laws of perspective, enables us to understand that the perceptible Universe exists as _a cl.u.s.ter of cl.u.s.ters, irregularly disposed_.

The "cl.u.s.ters" of which this Universal "_cl.u.s.ter of cl.u.s.ters_" consists, are merely what we have been in the practice of designating "nebulae"-and, of these "nebulae," _one_ is of paramount interest to mankind. I allude to the Galaxy, or Milky Way. This interests us, first and most obviously, on account of its great superiority in apparent size, not only to any one other cl.u.s.ter in the firmament, but to all the other cl.u.s.ters taken together. The largest of these latter occupies a mere point, comparatively, 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 sixteen secondaries, or planets-the Moon one of seventeen tertiaries, or satellites. The Galaxy, let me repeat, is but one of the _cl.u.s.ters_ which I have been describing-but one of the mis-called "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 a.s.sertion may at first appear to those unversed in Astronomy, still the astronomer himself has no hesitation in a.s.serting that we are _in the midst_ of that inconceivable host of stars-of suns-of systems-which const.i.tute the Galaxy. Moreover, not only have _we_-not only has _our_ Sun a right to claim the Galaxy as its own especial cl.u.s.ter, 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 cl.u.s.ter in question has, in reality, a certain general-_very_ general resemblance to the planet Saturn, with its encompa.s.sing 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 sh.o.r.e of the island-on that side of it which is nearest the constellation of the Cross and farthest from that of Ca.s.siopeia. 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 a.s.sume, 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 cl.u.s.ter 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 phaenomena 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 ma.s.s of the cl.u.s.ter. _No_ consideration could be better adapted to convey an idea of this cl.u.s.ter's stupendous extent.

If, with a telescope of high s.p.a.ce-penetrating power, we carefully inspect the firmament, we shall become aware of _a belt of cl.u.s.ters_-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 _cl.u.s.ter of cl.u.s.ters_. This belt is _The Universe_. Our Galaxy is but one, and perhaps one of the most inconsiderable, of the cl.u.s.ters which go to the const.i.tution of this ultimate, Universal _belt_ or _band_. The appearance of this cl.u.s.ter of cl.u.s.ters, to our eyes, _as_ a belt or band, is altogether a perspective phaenomenon of the same character as that which causes us to behold our own individual and roughly-spherical cl.u.s.ter, the Galaxy, under guise also of a belt, traversing the Heavens at right angles to the Universal one. The shape of the all-inclusive cl.u.s.ter is, of course _generally_, that of each individual cl.u.s.ter 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 ma.s.s-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 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 a.s.signed them, _a priori_, seem to me unanswerable; but, not to speak of these, _observation_ a.s.sures 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."[11] 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 pa.s.s, 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 attracted _in 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.

[11] Page 62.

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 _cl.u.s.ter of cl.u.s.ters_-a collection around which, on all sides, extend the immeasurable wildernesses of a s.p.a.ce _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 a.n.a.logical right to the inference that this perceptible Universe-that this cl.u.s.ter of cl.u.s.ters-is but one of _a series_ of cl.u.s.ters of cl.u.s.ters, 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 retinas a light-impression-or from there being no such emanation as light at all, in these unspeakably distant worlds-or, lastly, from the mere interval being so vast, that the electric tidings of their presence in s.p.a.ce, have not yet-through the lapsing myriads of years-been enabled to traverse that interval?

Have we any right to inferences-have we any ground whatever for visions such as these? If we have a right to them in _any_ degree, we have a right to their infinite extension.

The human brain has obviously a leaning to the "_Infinite_," and fondles the phantom of the idea. It seems to long with a pa.s.sionate fervor for this impossible conception, with the hope of intellectually believing it when conceived. What is general among the whole race of Man, of course no individual of that race can be warranted in considering abnormal; nevertheless, there _may_ be a cla.s.s of superior intelligences, to whom the human bias alluded to may wear all the character of monomania.

My question, however, remains unanswered:-Have we any right to infer-let us say, rather, to imagine-an interminable succession of the "cl.u.s.ters of cl.u.s.ters," or of "Universes" more or less similar?

I reply that the "right," in a case such as this, depends absolutely upon the hardihood of that imagination which ventures to claim the right. Let me declare, only, that, as an individual, I myself feel impelled to the _fancy_-without daring to call it more-that there _does_ exist a _limitless_ succession of Universes, more or less similar to that of which we have cognizance-to that of which _alone_ we shall ever have cognizance-at the very least until the return of our own particular Universe into Unity. _If_ such cl.u.s.ters of cl.u.s.ters exist, however-_and they do_-it is abundantly clear that, having had no part in our origin, they have no portion in our laws. They neither attract us, nor we them.

Their material-their spirit is not ours-is not that which obtains in any part of our Universe. They could not impress our senses or our souls.

Among them and us-considering all, for the moment, collectively-there are no influences in common. Each exists, apart and independently, _in the bosom of its proper and particular G.o.d_.

In the conduct of this Discourse, I am aiming less at physical than at metaphysical order. The clearness with which even material phaenomena are presented to the understanding, depends very little, I have long since learned to perceive, upon a merely natural, and almost altogether upon a moral, arrangement. If then I seem to step somewhat too discursively from point to point of my topic, let me suggest that I do so in the hope of thus the better keeping unbroken that chain of _graduated impression_ by which alone the intellect of Man can expect to encompa.s.s the grandeurs of which I speak, and, in their majestic totality, to comprehend them.

So far, our attention has been directed, almost exclusively, to a general and relative grouping of the stellar bodies in s.p.a.ce. Of specification there has been little; and whatever ideas of _quant.i.ty_ have been conveyed-that is to say, of number, magnitude, and distance-have been conveyed incidentally and by way of preparation for more definitive conceptions. These latter let us now attempt to entertain.

Our solar system, as has been already mentioned, consists, in chief, of one sun and sixteen planets certainly, but in all probability a few others, revolving around it as a centre, and attended by seventeen moons of which we know, with possibly several more of which as yet we know nothing. These various bodies are not true spheres, but oblate spheroids-spheres flattened at the poles of the imaginary axes about which they rotate:-the flattening being a consequence of the rotation.

Neither is the Sun absolutely the centre of the system; for this Sun itself, with all the planets, revolves about a perpetually shifting point of s.p.a.ce, which is the system's general centre of gravity. Neither are we to consider the paths through which these different spheroids move-the moons about the planets, the planets about the Sun, or the Sun about the common centre-as circles in an accurate sense. They are, in fact, _ellipses-one of the foci being the point about which the revolution is made_. An ellipse is a curve, returning into itself, one of whose diameters is longer than the other. In the longer diameter are two points, equidistant from the middle of the line, and so situated otherwise that if, from each of them a straight line be drawn to any one point of the curve, the two lines, taken together, will be equal to the longer diameter itself. Now let us conceive such an ellipse. At one of the points mentioned, which are the _foci_, let us fasten an orange. By an elastic thread let us connect this orange with a pea; and let us place this latter on the circ.u.mference of the ellipse. Let us now move the pea continuously around the orange-keeping always on the circ.u.mference of the ellipse. The elastic thread, which, of course, varies in length as we move the pea, will form what in geometry is called a _radius vector_. Now, if the orange be understood as the Sun, and the pea as a planet revolving about it, then the revolution should be made at such a rate-with a velocity so varying-that the _radius vector_ may pa.s.s over _equal areas of s.p.a.ce in equal times_. The progress of the pea _should be_-in other words, the progress of the planet _is_, of course,-slow in proportion to its distance from the Sun-swift in proportion to its proximity. Those planets, moreover, move the more slowly which are the farther from the Sun; _the squares of their periods of revolution having the same proportion to each other, as have to each other the cubes of their mean distances from the Sun_.

The wonderfully complex laws of revolution here described, however, are not to be understood as obtaining in our system alone. They _everywhere_ prevail where Attraction prevails. They control _the Universe_. Every shining speck in the firmament is, no doubt, a luminous sun, resembling our own, at least in its general features, and having in attendance upon it a greater or less number of planets, greater or less, whose still lingering luminosity is not sufficient to render them visible to us at so vast a distance, but which, nevertheless, revolve, moon-attended, about their starry centres, in obedience to the principles just detailed-in obedience to the three omniprevalent laws of revolution-the three immortal laws _guessed_ by the imaginative Kepler, and but subsequently demonstrated and accounted for by the patient and mathematical Newton. Among a tribe of philosophers who pride themselves excessively upon matter-of-fact, it is far too fashionable to sneer at all speculation under the comprehensive _sobriquet_, "guess-work." The point to be considered is, _who_ guesses. In guessing with Plato, we spend our time to better purpose, now and then, than in hearkening to a demonstration by Alcmaeon.

In many works on Astronomy I find it distinctly stated that the laws of Kepler are _the basis_ of the great principle, Gravitation. This idea must have arisen from the fact that the suggestion of these laws by Kepler, and his proving them _a posteriori_ to have an actual existence, led Newton to account for them by the hypothesis of Gravitation, and, finally, to demonstrate them _a priori_, as necessary consequences of the hypothetical principle. Thus so far from the laws of Kepler being the basis of Gravity, Gravity is the basis of these laws-as it is, indeed, of all the laws of the material Universe which are not referable to Repulsion alone.

The mean distance of the Earth from the Moon-that is to say, from the heavenly body in our closest vicinity-is 237,000 miles. Mercury, the planet nearest the Sun, is distant from him 37 millions of miles. Venus, the next, revolves at a distance of 68 millions:-the Earth, which comes next, at a distance of 95 millions:-Mars, then, at a distance of 144 millions. Now come the eight Asteroids (Ceres, Juno, Vesta, Pallas, Astraea, Flora, Iris, and Hebe) at an average distance of about 250 millions. Then we have Jupiter, distant 490 millions; then Saturn, 900 millions; then Ura.n.u.s, 19 hundred millions; finally Neptune, lately discovered, and revolving at a distance, say of 28 hundred millions.

Leaving Neptune out of the account-of which as yet we know little accurately and which is, possibly, one of a system of Asteroids-it will be seen that, within certain limits, there exists an _order of interval_ among the planets. Speaking loosely, we may say that each outer planet is twice as far from the Sun as is the next inner one. May not the _order_ here mentioned-_may not the law of Bode-be deduced from consideration of the a.n.a.logy suggested by me as having place between the solar discharge of rings and the mode of the atomic irradiation_?

The numbers hurriedly mentioned in this summary of distance, it is folly to attempt comprehending, unless in the light of abstract arithmetical facts. They are not practically tangible ones. They convey no precise ideas. I have stated that Neptune, the planet farthest from the Sun, revolves about him at a distance of 28 hundred millions of miles. So far good:-I have stated a mathematical fact; and, without comprehending it in the least, we may put it to use-mathematically. But in mentioning, even, that the Moon revolves about the Earth at the comparatively trifling distance of 237,000 miles, I entertained no expectation of giving any one to understand-to know-to feel-how far from the Earth the Moon actually _is_. 237,000 _miles_! There are, perhaps, few of my readers who have not crossed the Atlantic ocean; yet how many of them have a distinct idea of even the 3,000 miles intervening between sh.o.r.e and sh.o.r.e? I doubt, indeed, whether the man lives who can force into his brain the most remote conception of the interval between one milestone and its next neighbor upon the turnpike. We are in some measure aided, however, in our consideration of distance, by combining this consideration with the kindred one of velocity. Sound pa.s.ses through 1100 feet of s.p.a.ce in a second of time. Now were it possible for an inhabitant of the Earth to see the flash of a cannon discharged in the Moon, and to hear the report, he would have to wait, after perceiving the former, more than 13 entire days and nights before getting any intimation of the latter.

However feeble be the impression, even thus conveyed, of the Moon's real distance from the Earth, it will, nevertheless, effect a good object in enabling us more clearly to see the futility of attempting to grasp such intervals as that of the 28 hundred millions of miles between our Sun and Neptune; or even that of the 95 millions between the Sun and the Earth we inhabit. A cannon-ball, flying at the greatest velocity with which such a ball has ever been known to fly, could not traverse the latter interval in less than 20 years; while for the former it would require 590.

Our Moon's real diameter is 2160 miles; yet she is comparatively so trifling an object that it would take nearly 50 such orbs to compose one as great as the Earth.

The diameter of our own globe is 7912 miles-but from the enunciation of these numbers what positive idea do we derive?

If we ascend an ordinary mountain and look around us from its summit, we behold a landscape stretching, say 40 miles, in every direction; forming a circle 250 miles in circ.u.mference; and including an area of 5000 square miles. The extent of such a prospect, on account of the _successiveness_ with which its portions necessarily present themselves to view, can be only very feebly and very partially appreciated:-yet the entire panorama would comprehend no more than one 40,000th part of the mere _surface_ of our globe. Were this panorama, then, to be succeeded, after the lapse of an hour, by another of equal extent; this again by a third, after the lapse of another hour; this again by a fourth after lapse of another hour-and so on, until the scenery of the whole Earth were exhausted; and were we to be engaged in examining these various panoramas for twelve hours of every day; we should nevertheless, be 9 years and 48 days in completing the general survey.

But if the mere surface of the Earth eludes the grasp of the imagination, what are we to think of its cubical contents? It embraces a ma.s.s of matter equal in weight to at least 2 s.e.xtillions, 200 quintillions of tons. Let us suppose it in a state of quiescence; and now let us endeavor to conceive a mechanical force sufficient to set it in motion! Not the strength of all the myriads of beings whom we may conclude to inhabit the planetary worlds of our system-not the combined physical strength of _all_ these beings-even admitting all to be more powerful than man-would avail to stir the ponderous ma.s.s _a single inch_ from its position.

What are we to understand, then, of the force, which under similar circ.u.mstances, would be required to move the _largest_ of our planets, Jupiter? This is 86,000 miles in diameter, and would include within its periphery more than a thousand orbs of the magnitude of our own. Yet this stupendous body is actually flying around the Sun at the rate of 29,000 miles an hour-that is to say, with a velocity 40 times greater than that of a cannon-ball! The thought of such a phaenomenon cannot well be said to _startle_ the mind:-it palsies and appals it. Not unfrequently we task our imagination in picturing the capacities of an angel. Let us fancy such a being at a distance of some hundred miles from Jupiter-a close eye-witness of this planet as it speeds on its annual revolution. Now _can_ we, I demand, fashion for ourselves any conception so distinct of this ideal being's spiritual exaltation, as _that_ involved in the supposition that, even by this immeasurable ma.s.s of matter, whirled immediately before his eyes, with a velocity so unutterable, he-an angel-angelic though he be-is not at once struck into nothingness and overwhelmed?

At this point, however, it seems proper to suggest that, in fact, we have been speaking of comparative trifles. Our Sun, the central and controlling orb of the system to which Jupiter belongs, is not only greater than Jupiter, but greater by far than all the planets of the system taken together. This fact is an essential condition, indeed, of the stability of the system itself. The diameter of Jupiter has been mentioned:-it is 86,000 miles:-that of the Sun is 882,000 miles. An inhabitant of the latter, travelling 90 miles a day, would be more than 80 years in going round a great circle of its circ.u.mference. It occupies a cubical s.p.a.ce of 681 quadrillions, 472 trillions of miles. The Moon, as has been stated, revolves about the Earth at a distance of 237,000 miles-in an orbit, consequently, of nearly a million and a half. Now, were the Sun placed upon the Earth, centre over centre, the body of the former would extend, in every direction, not only to the line of the Moon's...o...b..t, but beyond it, a distance of 200,000 miles.

And here, once again, let me suggest that, in fact, we have _still_ been speaking of comparative trifles. The distance of the planet Neptune from the Sun has been stated:-it is 28 hundred millions of miles; the circ.u.mference of its...o...b..t, therefore, is about 17 billions. Let this be borne in mind while we glance at some one of the brightest stars.

Between this and the star of _our_ system, (the Sun,) there is a gulf of s.p.a.ce, to convey any idea of which we should need the tongue of an archangel. From _our_ system, then, and from _our_ Sun, or star, the star at which we suppose ourselves glancing is a thing altogether apart:-still, for the moment, let us imagine it placed upon our Sun, centre over centre, as we just now imagined this Sun itself placed upon the Earth. Let us now conceive the particular star we have in mind, extending, in every direction, beyond the orbit of Mercury-of Venus-of the Earth:-still _on_, beyond the orbit of Mars-of Jupiter-of Ura.n.u.s-until, finally, we fancy it filling the circle-17 _billions of miles in circ.u.mference_-which is described by the revolution of Leverrier's planet. When we have conceived all this, we shall have entertained no extravagant conception. There is the very best reason for believing that many of the stars are even far larger than the one we have imagined. I mean to say that we have the very best _empirical_ basis for such belief:-and, in looking back at the original, atomic arrangements for _diversity_, which have been a.s.sumed as a part of the Divine plan in the const.i.tution of the Universe, we shall be enabled easily to understand, and to credit, the existence of even far vaster disproportions in stellar size than any to which I have hitherto alluded. The largest orbs, of course, we must expect to find rolling through the widest vacancies of s.p.a.ce.

I remarked, just now, that to convey an idea of the interval between our Sun and any one of the other stars, we should require the eloquence of an archangel. In so saying, I should not be accused of exaggeration; for, in simple truth, these are topics on which it is scarcely possible to exaggerate. But let us bring the matter more distinctly before the eye of the mind.

In the first place, we may get a general, _relative_ conception of the interval referred to, by comparing it with the inter-planetary s.p.a.ces.

If, for example, we suppose the Earth, which is, in reality, 95 millions of miles from the Sun, to be only _one foot_ from that luminary; then Neptune would be 40 feet distant; _and the star Alpha Lyrae, at the very least_, 159.

Now I presume that, in the termination of my last sentence, few of my readers have noticed anything especially objectionable-particularly wrong. I said that the distance of the Earth from the Sun being taken at _one foot_, the distance of Neptune would be 40 feet, and that of Alpha Lyrae, 159. The proportion between one foot and 159 has appeared, perhaps, to convey a sufficiently definite impression of the proportion between the two intervals-that of the Earth from the Sun and that of Alpha Lyrae from the same luminary. But my account of the matter should, in reality, have run thus:-The distance of the Earth from the Sun being taken at one foot, the distance of Neptune would be 40 feet, and that of Alpha Lyrae, 159--_miles_:-that is to say, I had a.s.signed to Alpha Lyrae, in my first statement of the case, only the 5280_th_ _part_ of that distance which is the _least distance possible_ at which it can actually lie.

To proceed:-However distant a mere _planet_ is, yet when we look at it through a telescope, we see it under a certain form-of a certain appreciable size. Now I have already hinted at the probable bulk of many of the stars; nevertheless, when we view any one of them, even through the most powerful telescope, it is found to present us with _no form_, and consequently with _no magnitude_ whatever. We see it as a point and nothing more.

Again;-Let us suppose ourselves walking, at night, on a highway. In a field on one side of the road, is a line of tall objects, say trees, the figures of which are distinctly defined against the background of the sky. This line of objects extends at right angles to the road, and from the road to the horizon. Now, as we proceed along the road, we see these objects changing their positions, respectively, in relation to a certain fixed point in that portion of the firmament which forms the background of the view. Let us suppose this fixed point-sufficiently fixed for our purpose-to be the rising moon. We become aware, at once, that while the tree nearest us so far alters its position in respect to the moon, as to seem flying behind us, the tree in the extreme distance has scarcely changed at all its relative position with the satellite. We then go on to perceive that the farther the objects are from us, the less they alter their positions; and the converse. Then we begin, unwittingly, to estimate the distances of individual trees by the degrees in which they evince the relative alteration. Finally, we come to understand how it might be possible to ascertain the actual distance of any given tree in the line, by using the amount of relative alteration as a basis in a simple geometrical problem. Now this relative alteration is what we call "parallax;" and by parallax we calculate the distances of the heavenly bodies. Applying the principle to the trees in question, we should, of course, be very much at a loss to comprehend the distance of _that_ tree, which, however far we proceeded along the road, should evince _no_ parallax at all. This, in the case described, is a thing impossible; but impossible only because all distances on our Earth are trivial indeed:-in comparison with the vast cosmical quant.i.ties, we may speak of them as absolutely nothing.

Now, let us suppose the star Alpha Lyrae directly overhead; and let us imagine that, instead of standing on the Earth, we stand at one end of a straight road stretching through s.p.a.ce to a distance equalling the diameter of the Earth's...o...b..t-that is to say, to a distance of 190 _millions of miles_. Having observed, by means of the most delicate micrometrical instruments, the exact position of the star, let us now pa.s.s along this inconceivable road, until we reach its other extremity.