THE SCENERY OF THE SKIES.
THE publication of. Mr. Lockyer's admirable translation of M. Amedde Guillemin's splendidly illustrated handbook of popular astronomy,* is quite an era in the art of popularizing that most exciting of sciences. We have only to complain of the physical magnitude of this edition, which is so considerable that we are not quite sure whether it may not be a visible object, or what astronomers call a test-object, to lunarian astronomers. At all events, if the publisher had sent us an easel fitted with a reading frame, by which to adapt it to the mechanical and optical condi- tions of humanity, he would certainly have put it more within the reach of invalids. Seriously speaking, in any new edition it should at least be broken up into two volumes. The mechanical fatigue of holding the book, certainly absorbs a considerable portion of the nervous energy needed to enter into the brilliant pictures sum- moned up by its contents. Nevertheless no book has ever been published calculated in an equal degree to realize the different astronomical spectacles of the Heavens to the mind of an ordinary reader.
The most carious point which strikes us in considering the external scenery of the skies as it could be seen at least by human eyes, is that in all parts both of our own solar system and of other systems, so far as we can infer anything concerning them from telescopic observation, the grandest stations for obtain- ing knowledge of what is going on in the Heavens, and also for the multiplicity and gorgeousness of the spectacles there visible, are the subordinate stations, the stations on planets being the only ones probably from which astronomy could be studied at all, and the stations on planets' planets, that is on satellites, being usually far superior in the variety and splendour of their astronomical phe- nomena to those on the planets themselves. Professor Whewell, as is well known, made ingenious use of the peculiar charac- teristic of central suns,—the probable intensity of light and also of heat in which they exist, and the certainty that if they are habitable at all by any beings like those of earth, it can only be through the interposition of some very thick atmosphere or cloud-envelope between the external envelope of fire and the nucleus of the sun, which would of course be a veil through which sight could hardly penetrate,—to argue that the earth may be really the only inhabited body in the whole physical universe. For if all the glorious myriads of visible bodies, he argued, are clearly unfit for physical beings, it requires very much less effort to believe that the vast majority of secondary or plane- tary bodies are not so either, a conclusion which he tried to con- firm with respect to the planetary bodies of our own system by first depopulating the moon on account of its no-atmosphere, and then finding fault with Venus and Mercury as being too hot, with Mars, Jupiter, Saturn, and the others as being too cold, and pro- bably also too fluid, for the dwelling-place of creatures with bodies at all like our own. We confess the argument has always seemed to us at once arrogant and feeble. But we may adopt thus much of it pretty safely, —that self-luminous bodies are not likely to be good stations for observing (with any eyes like our own) other self-luminous bodies, and that even of those which only reflect light, the attendants on greater bodies
have special advantages over those greater bodies themselves, . for nearly the same reason for which the disciple has a special happiness denied to his master, for which Boswell has, a grander constant spectacle before him than Johnson, or Ecker- mann than Goethe.
Thus even our own moon, in many respects very inferior in advantages to the satellites of the more distant planets, must, if she have astronomers at all, — astronomers without lungs
they must be, at least on the hither aide of the moon,—have far more splendid astronomical opportunities for them than we
can get for the best of our astronomers, even on the Peak of Teneriffe. We do not insist upon the want of atmosphere,—in itself an immense advantage for star-gazing, which enables the lunarians to see the stars even at midday, and disposes of all the annoyance of unseasonable clouds and of " the error of refrac- tion,"—for perhaps few satellites except our own are without atmosphere, and there is plausibility in the argument that the absence of atmosphere, and consequently. of all water or fluid; in- volves a difference of constitution of such magnitude as to defeat all imagination as to the nature of the lunarians' or- ganization. But look only at the incentives to astronomy which the lunarians would have, if they exist at all, in having an earthlight, in the absence of the sun, fourteen times as splendid as our moonlight, and, moreover, one which begins, to inhabitants of this aide of the moon, to grow as sunlight
fades, and to diminish as annlight begins, an advantage which we have not, since our time of diurnal revolution is so much shorter
than that of the moon's that we often have nights without moon- light, while their long fortnight of darkness is—upon the near side of the moon—never without earthlight. Then what an incentive to astronomical observation would be the different astronomical phe- nomena of the two sides of the moon,—the one which is turned away from the earth never seeing the great earthlight at all, but having always a fortnight of uninterrupted night between the visits of the sun About 350 hours of continuous possibility of astronomical observation every fortnight, without liability to clouds or mists of any kind, on both sides of the moon, and an enormous lamp fourteen times the size of our moon, hung on one side to at- tract observation by its brilliant phases throughout the long night,
would certainly seem to be wonderful advantages for the astronomer. Yet the moon is one of the least remarkable points of observation among the satellites of our system. The nearest satellite of Jupiter (about the size of our moon), for instance, has in that planet a moon not 14 times the magnitude of our moon, but
320 times that magnitude, which is a light always waxing or waning during its night of not more than about 21 to 22 hours.
Besides this it has frequently the light of the other three subor-
dinate moons, all of which must be very brilliant when not at their greatest distance from it, and the frequent occultations or eclipses of the other satellites by each other and by the huge planet itself, which must occur so constantly as to acquire the sort of value as a measure of time which the motion of the hands' of a clock have for us. Hence the variety of brilliant astro- nomical phenomena occurring in the Jovian system is far greater and more exciting, especially to an inhabitant of one of the satellites, than is easy for us to conceive. Imagine 320 moons crowded together in one sky—dimly lit as we should think, it is
true, but as brilliantly lit in relation to the sunlight there as our moon is in relation to sunlight here—and this huge moon eclipsing almost every night one or more of three lesser moons, none of these insignificant, and we may imagine how much earlier the beings in Jupiter's satellites, if even as intelligent as ancient Egyptians, must have been provoked to study and systematize the motions of this great illuminated clock, with its one mighty hand and three little ones,—than the inhabitants of earth.
But even they had no incentive to astronomy to compare with observers, if observers there are, upon one of the rings or satellites of Saturn. It is true indeed that if the new theory as to the rings of Saturn have any foundation, a station on the rings of Saturn cannot be eligible to any person possessed of delicate chronometers, transit instruments, or other valuable astronomical weapons. For if it be true that the rings are nothing but mobs of satellites jostling each other in all direc-
tions, rushing like billiard-balls in pursuit of each other, now over- taking and running down a minor world, now overtaken and run down by a huge one,—then, no doubt, our Astronomer Royal would respectfully decline to permit the use even of his least valuable instruments in such an observatory as that, and Messrs. Cooke, the instrument-makers, would shut up shop there at once. But this is not true of the nearest of the satellites, Mimes ; and there are now believed to be some quite solitary mem-
hers of the mobs of satellites of Which the rings are composed, on the edges, interior and exterior, of each ring, which would be safe and most instructive situations for an observatory. To an observer in such a satellite on the interior edge of the interior ring, the spectacle of Saturn as a huge half-moon occupying one-eighth of the whole vault of heaven, must be inexpres- sibly magnificent. such an observer would of course see only half the planet,—the half above his own situation in the plane of the ring ; but as he would rotate round this huge planet in little more than ten hours, instead of taking a whole month to do it, like our lazy- moon, he would sea in about five hours this enormous half-crescent swelling into a half-moon, and then in five hours more diminishing again into invisibility. To aid the con- ception, imagine only seeing from St. Paul's a half-moon that should cover a whole eighth of the visible vault,—stretching over the sky so as to cover (say) the whole heavens behind and above the river, through all the reaches from Vauxhall Bridge to the Thames Tannel,—and seeing it grow so rapidly that in five hours it increased from a mere brilliant line, the arc of a quadrant on the horizon, to such a-mighty plain of light as this, and then dwindled again at the same rate. Moreover across this vast surface of light you would see the mighty belt of shadow cast by the rings, as the tourist on the Broeken sees his own gigantic shadow on the western clouds at break of day. And such an observer, when his mighty moon was setting and his own day coming, would almost invariably have to forego a large part of it, owing to the neces- sary solar eclipse which the great shadow of the planet would inflict upon him as he came round to face the sun. Then, if you suppose him to be at the same time a witness of the terrible game at bowls which is supposed to be the permanent condition of Saturn's rings, and which might make Rip van Winkle himself tremble, we may easily conceive that the astronomical phenomena with which we are acquainted are child's play to those witnessed by the astronomers of the Saturnian rings. There are besides eight outside moons, their phases, and their eclipses by the planet, to observe, in addition to the mighty planetary moon and its rings ; and the nearest to Saturn of these outside moons passes round the outer ring so rapidly that its motion minute by minute is more visible than that of the minute hand of a watch. Of all such marvels, M. Amedee Guillemin and his gorgeous illustrations give us a far more vivid conception than any popular handbook of astronomy known to us.
Nor is it only in our own system that the subordinate situation seem to have so great an advantage in astronomical opportunities, and variety of phenomena, over the central ones. There are other systems of which the book which has suggested this article tells us, in which planetary astronomers must have far more curious and complicated phenomena to observe, than any known to us even by inference. Take, for instance, the case of double or even triple stars, or sans, of different colours revolving round their common centre of gravity. On a planet of any one of these, you might have in one part of its course orange days, in another red, in another blue,—in another perhaps two or even three distinct dawns,--a yellow sun's dawn, a red sun's dawn, and a blue sun's dawn, the three colours blending when all were above the horizon, and making a yellowish white light; then on the setting (say) of the blue sun, leaving a yellowish crimson day, and on the setting of theyellow sun, a purely crimson daylight. In such a planet the nights would be of course rarely more than evening, as all three suns could hardly be invisible together. But what a variety of shades of feeling and association would be produced by the multiplicity of lights and combinations of light under which the landscapes of such a planet would be seen I Probably every additional external aid to the dis- crimination of seasons and periods would produce a new complexity of intellectual organization, and a planet with changes so various, with such cross-lights and cross-shadows of different colours, would, in all probability, have wholly different genera and species of plants and animaisfrom those of worlds in which the great agencyof light is uniform. To such a world we can imagine that Turner may have gone to receive, in addition to the one talent which his profound study of our poor colours had multiplied into ten, ten talents more. But the magnificence of the celestial scenery which such books as these suggest is far too great for the dimensions of any newspaper article, and we must leave our readers to refer to the magnificent work we have noticed, for hints of celestial scenery even more various and wonderful than any we have attempted to describe.