Chapter 16

The replies given to this query will be by no means unanimous. But, for the full understanding of the state of the main question, and to assist us in arriving at some sort of verdict, we will hear several authorities on both sides of the case. The evidence being cumulative, we pursue the chronological order, and begin with La Place. He writes: "The lunar atmosphere, if any such exists, is of an extreme rarity, greater even than that which can be produced on the surface of the earth by the best constructed air-pumps. It may be inferred from this that no terrestrial animal could live or respire at the surface of the moon, and that if the moon be inhabited, it must be by animals of another species." [428] This opinion, as Sir David Brewster points out, is not that the moon has no atmosphere, but that if it have any it is extremely attenuated. Mr. Russell Hind's opinion is similar with respect to water. He says: "Earlier selenographists considered the dull, grayish spots to be water, and termed them the lunar seas, bays, and lakes. They arc so called to the present day, though we have strong evidence to show that if water exist at all on the moon, it must be in very small quantity." [429] Mr. Grant tells us that "the question whether the moon be surrounded by an atmosphere has been much discussed by astronomers. Various phenomena are capable of indicating such an atmosphere, but, generally speaking, they are found to be unfavourable to its existence, or at all events they lead to the conclusion that it must be very inconsiderable." [430] Humboldt thinks that Schroeter's assumptions of a lunar atmosphere and lunar twilight are refuted, and adds: "If, then, the moon is without any gaseous envelope, the entire absence of any diffused light must cause the heavenly bodies, as seen from thence, to appear projected against a sky _almost black_ in the day-time. No undulation of air can there convey sound, song, or speech. The moon, to our imagination, which loves to soar into regions inaccessible to full research, is a desert where silence reigns unbroken." [431] Dr. Lardner considers it proven "that there does not exist upon the moon an atmosphere capable of reflecting light in any sensible degree," and also believes that "the same physical tests which show the non-existence of an atmosphere of air upon the moon are equally conclusive against an atmosphere of vapour." [432] Mr. Breen is more emphatic. He writes: "In the want of water and air, the question as to whether this body is inhabited is no longer equivocal. Its surface resolves itself into a sterile and inhospitable waste, where the lichen which flourishes amidst the frosts and snows of Lapland would quickly wither and die, and where no animal with a drop of blood in its veins could exist." [433] The anonymous author of the Essay on the _Plurality of Worlds_ announces that astronomers are agreed to negative our question without dissent. We shall have to manifest his mistake. His words are: "Now this minute examination of the moon's surface being possible, and having been made by many careful and skilful astronomers, what is the conviction which has been conveyed to their minds with regard to the fact of her being the seat of vegetable or animal life? Without exception, it would seem, they have all been led to the belief that the moon is not inhabited; that she is, so far as life and organization are concerned, waste and barren, like the streams of lava or of volcanic ashes on the earth, before any vestige of vegetation has been impressed upon them; or like the sands of Africa, where no blade of grass finds root." [434] Robert Chambers says: "It does not appear that our satellite is provided with an atmosphere of the kind found upon earth; neither is there any appearance of water upon the surface. . . . These characteristics of the moon forbid the idea that it can be at present a theatre of life like the earth, and almost seem to declare that it never can become so." [435] Schoedler's opinion is concurrent with what has preceded. He writes: "According to the most exact observations it appears that the moon has no atmosphere similar to ours, that on its surface there are no great bodies of water like our seas and oceans, so that the existence of water is doubtful. The whole physical condition of the lunar surface must, therefore, be so different from that of our earth, that beings organized as we are could not exist there." [436] Another German author says: "The observations of Fraunhofer (1823), Brewster and Gladstone (1860), Huggins and Miller, as well as Janssen, agree in establishing the complete accordance of the lunar spectrum with that of the sun. In all the various portions of the moon's disk brought under observation, no difference could be perceived in the dark lines of the spectrum, either in respect of their number or relative intensity. From this entire absence of any special absorption lines, it must be concluded that there is no atmosphere in the moon, a conclusion previously arrived at from the circumstance that during an occultation no refraction is perceived on the moon's limb when a star disappears behind the disk." [437] Mr. Nasmyth follows in the same strain. Holding that the moon lacks air, moisture, and temperature, he says, "Taking all these adverse conditions into consideration, we are in every respect justified in concluding that there is no possibility of animal or vegetable life existing on the moon, and that our satellite must therefore be regarded as a barren world." [438] A French astronomer holds a like opinion, saying: "There is nothing to show that the moon possesses an atmosphere; and if there was one, it would be perceptible during the occultations of the stars and the eclipses of the sun. It seems impossible that, in the complete absence of air, the moon can be peopled by beings organized like ourselves, nor is there any sign of vegetation or of any alteration in the state of its surface which can be attributed to a change of seasons." [439] On the same side Mr. Crampton writes most decisively, "With what we _do_ know, however, of our satellite, I think the idea of her being inhabited may be dismissed _summarily_; _i.e._ her inhabitation by intelligent beings, or an animal creation such as exist here." [440] And, finally, in one of Maunder's excellent _Treasuries_, we read of the moon, "She has no atmosphere, or at least none of sufficient density to refract the rays of light as they pass through it, and hence there is no water on her surface; consequently she can have no animals like those on our planet, no vegetation, nor any change of seasons." [441] These opinions, recorded by so many judges of approved ability and learning, have great weight; and some may regard their premisses and conclusions as irresistibly cogent and convincing. The case against inhabitation is certainly strong. But justice is impartial. _Audi alteram partem_.

Judges of equal erudition will now speak as respondents. We go back to the seventeenth century, and begin with a work whose reasoning is really remarkable, seeing that it is nearly two hundred and fifty years since it was first published. We refer to the _Discovery of a New World_ by John Wilkins, Bishop of Chester; in which the reverend philosopher aims to prove the following propositions:--"1. That the strangeness of this opinion (that the moon may be a world) is no sufficient reason why it should be rejected; because other certain truths have been formerly esteemed as ridiculous, and great absurdities entertained by common consent. 2. That a plurality of worlds does not contradict any principle of reason or faith. 3. That the heavens do not consist of any such pure matter which can privilege them from the like change and corruption, as these inferior bodies are liable unto. 4. That the moon is a solid, compacted, opacous body. 5. That the moon hath not any light of her own. 6. That there is a world in the moon, hath been the direct opinion of many ancient, with some modern mathematicians; and may probably be deduced from the tenets of others. 9. That there are high mountains, deep valleys, and spacious plains in the body of the moon. 10. That there is an atmosphoera, or an orb of gross vaporous air, immediately encompassing the body of the moon. 13. That 'tis probable there may be inhabitants in this other world; but of what kind they are, is uncertain." [442] We go on to 1686, and listen to the French philosopher, Fontenelle, in his Conversations with the Marchioness. "'Well, madam,' _said I_, 'you will not be surprised when you hear that the moon is an earth too, and that she is inhabited as ours is.' 'I confess,' _said she_, 'I have often heard talk of the world in the moon, but I always looked upon it as visionary and mere fancy.' 'And it may be so still,' _said I_. 'I am in this case as people in a civil war, where the uncertainty of what may happen makes them hold intelligence with the opposite party; for though I verily believe the moon is inhabited, I live civilly with those who do not believe it; and I am still ready to embrace the prevailing opinion. But till the unbelievers have a more considerable advantage, I am for the people in the moon.'" [443] Whatever may be thought of his philosophy, no one could quarrel with the Secretary of the Academy on the score of his politeness or his prudence. A more recent and more reliable authority appears in Sir David Brewster. He tells us that "MM. Maedler and Beer, who have studied the moon's surface more diligently than any of their predecessors or contemporaries, have arrived at the conclusion that she has an atmosphere." Sir David himself maintains that "_every planet and satellite in the solar system must have an atmosphere_." [444] Bonnycastle, whilom professor of mathematics in the Royal Military Academy, Woolwich, writes: "Astronomers were formerly of opinion that the moon had no atmosphere, on account of her never being obscured by clouds or vapours; and because the fixed stars, at the time of an occultation, disappear behind her instantaneously, without any gradual diminution of their light. But if we consider the effects of her days and nights, which are near thirty times as long as with us, it may be readily conceived that the phenomena of vapours and meteors must be very different. And besides, the vaporous or obscure part of our atmosphere is only about the one thousand nine hundred and eightieth part of the earth's diameter, as is evident from observing the clouds, which are seldom above three or four miles high; and therefore, as the moon's apparent diameter is only about thirty-one minutes and a half, or one thousand eight hundred and ninety seconds, the obscure part of her atmosphere, supposing it to resemble our own, when viewed from the earth, must subtend an angle of less than one second; which is so small a space, that observations must be extremely accurate to determine whether the supposed obscuration takes place or not." [445] Dr. Brinkley, at one time the Astronomer-Royal of Ireland, writes: "Many astronomers formerly denied the existence of an atmosphere at the moon; principally from observing no variation of appearance on the surface, like what would take place, did clouds exist as with us; and also, from observing no change in the light of the fixed stars on the approach of the dark edge of the moon. The circumstance of there being no clouds, proves either that there is no atmosphere similar to that of our earth, or that there are no waters on its surface to be converted into vapour; and that of the lustre of the stars not being changed, proves that there can be no dense atmosphere. But astronomers now seem agreed that an atmosphere does surround the moon, although of small density when compared with that of our earth. M. Schroeter has observed a small twilight in the moon, such as would arise from an atmosphere capable of reflecting the rays at the height of about one mile." [446] Dr. Brinkley is inaccurate in saying that astronomers are agreed as to the lunar atmosphere. Like students in every other department of inquiry, spiritual as well as physical, they fail at present to see "eye to eye"; which is not surprising, seeing that the eye is so restricted, and the object so remote.

Dr. Dick, whose productions have done much to popularize the study of the heavens, and to promote its reverent pursuit, says: "On the whole it appears most probable that the moon is surrounded with a fluid which serves the purpose of an atmosphere; although this atmosphere, as to its nature, composition, and refractive power, may be very different from the atmosphere which surrounds the earth. It forms no proof that the moon, or any of the planets, is destitute of an atmosphere, because its constitution, its density, and its power of refracting the rays of light are different from ours. An atmosphere may surround a planetary body, and yet its parts be so fine and transparent that the rays of light, from a star or any other body, may pass through it without being in the least obscured, or changing their direction. In our reasonings on this subject, we too frequently proceed on the false principle, that everything connected with other worlds must bear a resemblance to those on the earth." [447] Mr. Neison, who has written one of the latest contributions to the science of selenography, says, "Of the present non-existence of masses of water upon the surface of the moon, there remains no doubt, though no evidence of its entire absence from the lunar crust can be adduced; and similarly, many well-established facts in reference to the moon afford ample proof of the non-existence of a lunar atmosphere, having a density equal to, or even much less than, that of the earth; but of the absence of an atmosphere, whose mass should enable it to play an important part in the moulding of the surface of the moon, and comparable almost to that of the terrestrial atmosphere, in their respective ratios to the masses of their planets, little, if any, trustworthy evidence exists." On another page of the same work, the author affirms "that later inquiries have shown that the moon may possess an atmosphere that must be regarded as fully capable of sustaining various forms of vegetation of even an advanced type; and, moreover, it does not appear how it can justly be questioned that the lunar surface in favourable positions may yet retain a sufficiency of moisture to support vegetation of many kinds; whilst in a very considerable portion of the entire surface of the moon, the temperature would not vary sufficiently to materially affect the existence of vegetable life." [448] Some of these writers may appear to be travelling rather too fast or too far, and their assumptions may wear more of the aspect of plausibility than of probability. But on their atmospheric and aqueous hypothesis, vegetation in abundance is confessedly a legitimate consequence. If a recent writer has liberty to condense into a sentence the conclusion from the negative premiss in the argument by saying, "As there is but a little appearance of water or air upon the moon, the conclusion has been inferred that there exists no vegetable or animal life on that globe," [449] other writers, holding opposite views of the moon's physical condition, may be allowed to expatiate on the luxuriant life which an atmosphere with water and temperature would undoubtedly produce. Mr. Proctor's tone is temperate, and his language that of one who is conscious with Hippocrates that "art is long and life is short." He says, in one of his contributions to lunar science, "It may safely be asserted that the opportunities presented during the life of any single astronomer for a trustworthy investigation of any portion of the moon's surface, under like conditions, are few and far between, and the whole time so employed must be brief, even though the astronomer devote many more years than usual to observational research." [450] This prepares us to find in another of the same author's works the following suggestive sentence: "With regard to the present habitability of the moon, it may be remarked that we are not justified in asserting positively that no life exists upon her surface. Life has been found under conditions so strange, we have been so often mistaken in assuming that _here_ certainly, or _there_, no living creatures can possibly exist, that it would be rash indeed to dogmatise respecting the state of the moon in this respect." [451] Narrien, one of the historians of the science, may be heard, though his contribution might be cast into either scale. He writes: "The absence of those variations of light and shade which would be produced by clouds floating above her surface, and the irregularities of the ground, visible at the bottom and on the sides of her cavities, have given reason to believe that no atmosphere surrounds her, and that she is destitute of rivers and seas. Such are the opinions generally entertained concerning the moon; but M. Schroeter, a German astronomer, ventures to assert that our satellite is the abode of living and intellectual beings; he has perceived some indications of an atmosphere which, however, he admits, cannot exceed two miles in height, and certain elevations which appear to him to be works of art rather than of nature. He considers that a uniformity of temperature must be produced on her surface by her slow rotation on her axis, by the insensible change from day to night, and the attenuated state of her atmosphere, which is never disturbed by storms; and that light vapours, rising from her valleys, fall in the manner of a gentle and refreshing dew to fertilize her fields." [452] Dr. H. W. M. Olbers is fully persuaded "that the moon is inhabited by rational creatures, and that its surface is more or less covered with a vegetation not very dissimilar to that of our own earth." Dr. Gruithuisen, of Munich, maintains that he has descried through his large achromatic telescope "great artificial works in the moon erected by the lunarians," which he considers to be "a system of fortifications thrown up by the selenitic engineers." We should have scant hope of deciding the dispute by the dicta of the ancients, were these far more copious than we find them to be. Yet reverence for antiquity may justify our quoting one of the classic fathers. Plutarch says, "The Pythagoreans affirme, that the moone appeereth terrestriall, for that she is inhabited round about, like as the earth wherein we are, and peopled as it were with the greatest living creatures, and the fairest plants." Again, "And of all this that hath been said (my friend _Theon_) there is nothing that doth proove and show directly, this habitation of men in the moon to be impossible." [453] Here we close the argument based on _induction_, and sum up the evidence in our possession. On the one hand, several scientific men, whose names we need not repeat, having surveyed the moon, deny it an atmosphere, water, and other conditions of life. Consequently, they disbelieve in its inhabitation, solely because they consider the fact undemonstrable; none of them being so unscientific as to believe it to be absolutely impossible. On the other hand, we have the valuable views of Maedler and Beer, whose lunar labours are unsurpassed, and whose map of the moon is a marvel and model of advanced selenography. They do not suppose the conditions on our satellite to be exactly what they are on this globe. In their own words, the moon is "no copy of the earth, much less a colony of the same." They merely believe her to be environed with air, and thus habitable. And when we recall our own Sir David Brewster, Professor Bonnycastle, Dr. Brinkley, Dr. Dick, Mr. Neison, and Mr. Proctor; and reckon with them the continental astronomers, Dr. Gruithuisen, Dr. Olbers, and Schroeter, all of whom attempted to fix the idea of planetary inhabitation on the popular mind, we must acknowledge that they, with their opponents, have a strong claim on our attention. The only verdict we are able just now to render, after hearing these conflicting testimonies, is the Scotch one, _Not proven_. We but append the legal indorsement _ignoramus_, we do not know. The subject must remain _sub judice_; but what we know not now, we hope to know hereafter.