fore, offer it as a conjecture not quite arbitrary, | Venus and Mercury we see nothing of a gaseous that Jupiter is a mere sphere of water. or aqueous atmosphere." "The polar and equatorial diameters of Jupiter are in the proportion of 13 to 14. Now it is a remarkable circumstance that this is the amount of oblateness which, on mechanical principles, would result from his time of revolution if he were entirely fluid, and of the same density throughout. So far, then, we have some confirmation at least of his being composed entirely of some fluid which in its density agrees with water." (P. 281.) Here, however, astronomers of every grade are at issue with the advocate of extra-terrestial chaos. Every one who has made the planetary discs objects of close contemplation, has discerned in all of them features that can be due to nothing else than gaseous and vaporous coverings. Indications of a very dense atmosphere are discernible in Mars,-and Stripped of all that is irrelevant to the its snows, whose existence even the essayargument, the specific gravity and form ist seems to admit, must be allowed to be of Jupiter merely prove, in the first place, very mysterious accumulations, if these that the substance of that huge sphere is indications are deceptive. The atmoscomposed of something which is specifi-phere in Venus is believed to be twice as cally as light as water, and which may be, as Sir David Brewster remarks, coal, pumice-stone, amianthus or tabasheer, or, as the essayist himself naïvely suggests, ice—and in the second place, that that substance was most probably liquid at the time when the sphere assumed its form, much in the same way as is generally also held with regard to the Earth. The greater oblateness of Jupiter's spheroid is simply due to the greater velocity with which its equatorial region was whirled along, before it was fixed in consolidation. Jupiter is eleven times wider than the Earth, and yet rotates in ten hours instead of twenty-four. The high degree of probability is, that if the Earth had been as large as Jupiter, and had rotated as quickly, it would have been as oblate too, notwithstanding its greater density. The essayist fails altogether in his endeavor to show upon these premises that in "Jupiter and Saturn may be regarded as, many respects, immense clouds; the continuous water being collected at their centres, while the more airy and lesser parts circulate above. That they are the permanent receptacles of the superfluous water and air of the system. . . .. Examples of what glorious objects accumulations of vapor and water, illuminated by the rays of the sun, may become in our eyes." (P. 309.) The essayist deems the smaller and denser planets, bodies that are devoid altogether of atmospheres, with the probable exception of Mars. "Mars seems to have some portion at least of aqueous atmosphere [in another place-perhaps we are not quite certain about the existence of an atmosphere]; the Earth, we know, has a considerable atmosphere of air and of vapor; but the Moon, so near to her mistress, has none, On dense as the Earth's. The strange, undefined, and confused glare of its outline is not explicable upon any other ground, and then too its narrow crescent, when it is nearly between the Earth and the Sun, is twice as broad as, and perceptibly longer than, it would be if there were no atmosphere; its horns of light extend considerably beyond the half circumference. Very accurate observers have actually seen the fringe of twilight resting upon its surface between broad daylight and earth-shine. The variable cloudbelts of Jupiter and Saturn have not even been challenged by the skeptical essayist; and his firmest support in this particular, the Moon, is in danger of disappearing be neath his feet. Sir John Herschel thinks that there are traces of a faint atmosphere in the lunar valleys and on its lowest plains. Baer and Mäedler, who have literally identified their names with selenography by their patient and close watching of the physical appearances of the terrestial satellite, are of the opinion that it has an aërial envelope proportioned to the smallness of its mass. Schroeter states that he can discern twilight on its surface at the extremities of its cusps, when in its crescent, and he limits the height of the aërial stratum to a third of a mile, which is considerably less than the altitude of the greater part of its mountains. This closely agrees with Sir John Herschel's idea of a little air settling as a sort of gaseous sea into the hollows and channels of the Moon, in the place of water, and quite accounts for the extreme difficulty that is experienced in detecting it by optical phenomena. If Encke is right in filling otherwise void space with some resisting ethereal medium, and if the zodiacal light is substantial, it is not possible that the Moon should have done otherwise than gather some of the ponderable material as a vaporous garment round its attractive mass. A recent discovery of Professor Hansen's, noticed by Professor Baden Powell, suggests how cautious men of science should be in coming even to negative conclusions on first appearances. In studying the inequalities of the Moon's movements, in connection with the theory of gravitation, this careful investigator has found cause to suspect that the centre of gravity of the Moon is further than the centre of its figure from the Earth; in other words, that the side of the Moon towards the Earth is raised into a table-land, twentynine miles higher above the centre of gravity than the opposite hemisphere is. This at once explains the probable mechanism by which the same side of the Moon is steadily retained looking earthwards. But it at the same time renders it possible that there may be a deep ocean and a collection of dense air on the other side of the lunar sphere, where they can never be contemplated by terrestial eyes. It is manifest that if such a distribution of solid material has really been made in the Moon, as Professor Hansen describes, water and air would have run down to that lower side, and filled up its twenty-nine miles of comparative depression, before they began to make their appearance on the nearer surface. If these calculations and views be correct, the Moon, instead of being uninhabited, may possibly be half in barren desolation, and half luxuriant and life-colored, its desolate hemisphere looking unvaryingly towards the Earth, and its peopled one directed towards skies out of which the terrestial face never shines. Before we pass on from the consideration of such portions of the argument as are avowedly based upon physical evidence, to express our own views and convictions in the matter, we feel constrained to direct attention to certain peculiarities of the Essay, which are affairs rather of manner than substance, but which nevertheless, after the most liberal allowance has been made for the license of advocacy, still leave us with the sense of painful surprise and regret - surprise and regret that one who has so much of earnestness and subtle intellectual power at his command as the essayist manifestly has, should nevertheless have deemed it right to employ in grave argument such wea pons as we here perceive in use. We allude, in the first place, to the looseness with which the conclusions of the reasoning are in many cases drawn, and to the levity with which alternatives to them are suggested immediately afterwards; and, in the second place, to the specious way in which obvious truth is often warped until the very bounds of honesty are pressed. The first peculiarity seems to have struck Sir David Brewster as well as ourselves, for it is incidentally and directly alluded to in the following extract from "More Worlds than One": "The essayist pronounces it 'tolerably certain that Jupiter's density is not greater than it would be if his entire globe were composed of water;' and he concludes that Jupiter must therefore be that there is much evidence against the existence He afterwards states a mere sphere of water. of solid land' in that planet; but in opposition to this evidence, he subsequently contributes a few cinders at the centre-articles doubtless of peculiar value and interest where every thing else is water. The existence of cinders, however, where there is no heat, and where, as we shall presently see, the water is ice, must have perplexed his by telling us that the waters in Jupiter are bot and hence he wisely withdraws them, tomless,' that is, without a nucleus of cinders." (Brewster, p. 234.) chemistry; 6 The following extracts are from the anonymous essay: "It is also possible that the Creator should, on another planet, have established creatures of the nature of corals and molluscs, saurians and iguanodons, without having yet arrived at the period of intelligent creatures; especially if that other planet have longer years, a colder climate, a smaller mass, and perhaps no atmosphere. It is also possible that he should have put that smaller planet near the Earth, resembling it in some respects, as the Moon does, but without any inhabitants, as she has none; and that Mars may be such a planet." (P. 292.) "For such reasons, then, as were urged he has no inhabitants, or that they are aqueous, in the case of Jupiter, we must either suppose that gelatinous creatures, too, sluggish almost to be deemed alive, floating in their ice-cold waters, shrouded for ever by their humid skies." (P. 289.) "That none but masses of this size, and many far below this, are found outside of Mars, appears to indicate that the planet-making powers which and which produced the great globe of the Earth, were efficacious to this distance from the Sun, were, beyond this point, feebler; so that they could only give birth to smaller masses, to planetoids, to satellites, and to meteoric stones. Perhaps we may describe this want of energy in the planetmaking power, by saying that, at so great a distance from the central fire, there was not heat enough to melt together these smaller fragments into a larger globe, or, rather, when they existed in a nebular, perhaps in a gaseous state, that there was not heat enough to keep them in that state until the attraction of the parts of all of them had drawn them into one mass, which might afterwards solidify into a single globe." (P. 305.) These several instances involuntarily suggest the suspicion that the essayist is ever ready to shift his ground if it occurs to him that some new position may prove more advantageous to his cause than the old one. It seems as if water or ice were the same in Jupiter, since neither promised a comfortable or convenient home for intelligent creatures. As if Mars would do just as well with saurians or iguanodons as without them, if a case be but made out against men. As if the minor bodies of the solar system might be indebted either to stubborn solidity that would not melt, or to gaseous intractability that would condense too soon, so that they but acquiesce in the sentence of uninhabitability passed upon them. In one place the essayist writes: "Moreover, if you allow all the small planets between Mars and Jupiter to be uninhabited, the planetary bodies, which you acknowledge to be probably uninhabited, far outnumber those with regard to which even the most resolute pluralists of worlds hold to be inhabited. The majority swells every year. Since the publication of the Essay three have been added. The Planetoids are now twenty-nine. The fact of a planet being inhabited, then, is, at any rate, rather the exception than the rule; and, therefore, must be proved in each case by special evidence." (P. 28.) In another place the following graph appears: failed in the making," he is not entitled to speak of them, when it suits his purpose, as the majority of the planets, in order that he may establish the absence of life in such a majority! In his argument derived from geology the essayist says: "Not entire resemblance, but universal difference, is what we discover [in creation]: not the cases perpetually dissimilar, presents itself; not repetition of exactly similar cases, but a series of constancy, but change, perhaps advance; not one permanent and pervading scheme, but preparation and completion of successive schemes; not uniformity, and a fixed type of existences, but progression and a climax... ... If, then, the Earth the oasis in the desert of our system, there is nobe the sole inhabited spot in the work of creation, thing in this contrary to the analogy of creation. But if, in some way which perhaps we cannot discover, the earth obtained for accompaniments mere chaotic and barren masses as conditions of its coming into its present state; as it may have required for accompaniments the brute and imperfect races of former animals as conditions of coming into its present state as the habitation of man; the analogy is against and not in favor of, the belief that they too [the other masses, the planets, &c.] are habitations." (P. 198.) Here the essayist imagines a countless myriad of void deserts, all uniform in their desolation, in order that the law of universal difference may be observed by their being unlike to the inhabited Earth. Having one white ball, he makes 999,999 black ones, and speaks of himself as having effected variety. It is hardly conceivable that when writing this the writer of the Essay did not feel the law of universal variety really to require that all the orbs of space should be inhabited by creatures of different natures and kinds, in order that the predicament of uniformpara-ity in desolation might be escaped from, "The coincidence of the orbits (of the planet oids) has suggested to astronomers the conjecture that they have resulted from the explosion of a larger body, and from its fracture into fragments. Perhaps the general phenomena of the universe suggest rather the notion of a collapse of portions of sidereal matter than of a sudden disruption and dispersion of any portion of it; and these small bodies may be the results of some imperfectly effected concentration of the elements of our system, which, if it had gone on more completely and regularly, might have produced another planet like Mars or Venus." (P. 293.) Surely if the essayist holds that the planetoids are the "bits of a planet that The essayist argues that as the seas and continents of the Earth have been wasted during long ages upon mere brute life, it is probable that the seas and continents of other planets are occupied at the present time with a life no higher, or with no life at all. But surely he feels that through the early stages of its physical history the Earth was really undergoing a gradual and that therefore, if the planets are now preparation to become what it now is, in the same condition, analogy indicates as the probability that they too are preparing for the reception of higher organic developments. If the waste of the planets is such as the waste of the Earth was, there can be no doubt that that waste argues not against, but for, a plurality of worlds. The essayist speaks of man as being the "special care" of the Creator. Surely he believes that the sparrow and the lilies of the field are in their way as carefully provided for and guarded as the lord of creation. Indeed, in many particulars the instinctive creatures seem to have been more immediately the care of Providence than the rational one, to whom a wider license for following his own devices has been allowed. The radical mistake which runs throughout the argument of this Essay seems to us to be the attempt to adduce positive evidence that the planets and stars are chaotic and rude. In this attempt the author entirely fails. If he had rested satisfied with the position that, in the present state of human knowledge, there is no direct physical proof of the planets and stars being inhabited worlds, and that consequently all who are inclined to hold opposite opinions, upon religious or other grounds, are quite as much entitled to do so as the pluralists are to entertain their doctrines, there would have been scarcely any one inclined to dispute the proposition with him. When, however, instead of this course, he undertakes to show that "the belief that other planets as well as the Earth are the seats of habitation of living things has been entertained in general, not in consequence of physical reasons, but in spite of physical reasons," the affair is altogether changed. It is true that matter of fact is as much out of court on one side as it is on the other, and will continue to be so until cities as well as plains can be contemplated in the Moon; Esquimaux as well as snows in Mars; waving trees and creeping things, as well as twilight, in Venus; and living creatures, whether pigmies or monsters, as well as clouds, on the temperate spheres of those giants of the system, Jupiter and Saturn. Not so, however, with matters of probability. There are "physical reasons" why it is probable in the highest degree that the planets, at least, are inhabited worlds, and there are metaphysical reasons why it is improbable in the highest degree that they are waste desolation and chaos. Viewed merely as a simple probability, based upon the ground that the Earth itself is peopled with living things, the case is a very strong one. Captain Jacob has put this in a very clear light in his "Few More Words." His remarks are to the following effect: Let there be an urn containing 1000 balls of an unknown color shaken up together, and from this urn let one be drawn promiscuously, and be found to be black. The probability, in accordance with the doctrines established by Professor de Morgan, is 1000 to 999 that all the other balls contained in the urn are black too. The mere fact that a black ball has been caught hold of, the first time of dipping, marks this likelihood. This is the case of the pluralists, who maintain that because they have one planet that is inhabited, therefore all the other planets are inhabited too; and that because they have one sun that is attended by planets, therefore other suns have a similar attendance. They are as likely as not to be right. On the other hand the probability that the black ball which is drawn is the only one of that color that had been contained in the urn, is as one to one thousand. It is unlikely, in this degree, that the only black ball should have been caught hold of at the first dip out of such a multitude. This is the case of the essayist, who asserts that the Earth is the only inhabited planet, and that the solar system stands alone in the universe. He is one thousand times more likely to be wrong than to be right. These strong probabilities, however, become very much stronger, in each direction, when the force of certain obvious "physical reasons" is added to them. In the detailed arrangements of this only world, of whose condition man has any positive experience, it is found that the vast gaseous accumulation, which is denominated the vapor-sphere or atmosphere, is in various ways intimately connected with the series of transforma tions and changes that constitute life in its widest sense. The substance of the air is composed of the particular material atoms that are mainly employed in the work of organic fabrication, and those atoms are placed in it in such a state of loose relative connection that they are peculiarly available for the purpose. Air, indeed, is organizable substance in a readi ly organizable condition. Plants, and all vegetable productions, which constitute the ultimate nourishment of animal bodies, are made of the gases and vapors of the atmosphere. A fifth part of the atmo sphere is the stimulating influence which is immediately concerned in setting up and maintaining the corrosive decomposition of organized fabric, out of which animal capacities and powers are educed. It receives into itself the gaseous and vaporous products of this decomposition, and fits them for reörganization, in order that they may be economically used over again. The atmosphere, in short, is the great reservoir from which the material of life is immediately derived, and into which the waste of life is thrown, and at the same time it is the prime agent by whose instrumentality the operations of life are set going. It is the medium which stands between and connects the opposite extremes of vegetable and animal existence, which adapts each to the necessities of the other, and which makes each possible. Wherever there is air on the earth vital phenomena manifest themselves; whenever air is absent every kind of vital operation stops. So intimately, indeed, within the sphere of human observation and experience, are life and air invariably connected, that it becomes altogether impossible to separate them in thought. Each seems as much adapted to the other as the eye is adapted to light, or as light to the eye-they are in fact correlated terms, so closely associated that they cannot be dissevered by the mind. Whenever the idea of one is called up, notions of the other are presented with it, as necessarily involved. stronger reasons for its abandonment are brought forward than any that have been adduced in the "Essay." But if the Plurality of Worlds be admitted to be so likely and rational an assumption as to be entitled to rank henceforth amongst the dogmas of science, it by no means follows that the vital arrangements in other worlds are the exact counterparts of those which obtain upon the earth. Every consideration, on the other hand, points to a higher probability that there would be as great a diversity in worlds as there is in the creatures coëxistent with man upon this globe. There is no reason why five senses should limit the impressions of intelligence on percipient organization; there is no reason why four limbs should be the only pieces of active apparatus that bodies with backbones can wield. So far as the series of discovered planets that are associated with the earth are concerned, it is obvious that there are in them the several varieties of physical condition which would be most availably met by corresponding varieties of organic contrivance. The brief and hot seasons, bright atmosphere, dense glare, and moderate mass and dimensions of Venus seem to ask for different details of organization from such as would be most suitable to the short days, subdued sunshine, softened and unvaryingly temperate seasons, and large masses and dimensions of Jupiter and Saturn. highest probability is, not that there are men in the planets and stars, but that each planet and star has its own wondrous cat The It follows from these relations that if men looked out into the space which surrounds the earth, and saw upon some re-alogue of created vitalities, adapted to its mote orb floating in it trees and shrubs, and quadrupeds and creeping things, they would also believe in the presence there of air. Could any one beholding such forms do otherwise? Such presence would manifestly be taken as a matter of course, and not even questioned. But when they look into space they see orbs that are invested with gaseous and vaporous atmospheres, and by a reversal of the process they believe in the presence of living creatures. They accept the correlation as a matter of course, just as they would in the other case, and do not even make it a subject for question, until some skeptical essay is compiled to challenge their faith. This is why it is that the Plurality of Worlds is a popular, as well as a highly probable doctrine; and this is why it may and will continue to be held until own peculiarities of construction, constitution, and position. The highest probability is, that in this way, and not by the multiplication of desolation, the requirements of the essayist's law of "universal difference" are met. It may be all very well to limit the question to the consideration of "human life" when it is felt as a preliminary to entering upon the investigation that "one school of moral discipline, one theatre of moral action, and one arena of moral contests for the highest prizes, is a sufficient centre for innumerable hosts of stars and planets." But when this is not felt as a preliminary, the question of necessity assumes a far wider scope, and a much grander significance. Professor Owen has contributed a very interesting argument for the existence of a plurality of worlds in this wider sense, derived |