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Good Words 1860
The Moon's Invisible Side

An artistic eye can readily discover, amidst much diversity, the pervading style of a great master. The architect may display his skill in very varied forms. The private dwelling, the public sanctuary, and the monumental pile may all betray the genius of one presiding mind. There may be the utmost diversity of purpose, at the same time that there is a perfect unity of style. In the universe of worlds, it is not necessary to detect a sameness of purpose, in order to recognise the hand of the one great Archi-tect. We do not require to prove that the moon is inhabited, in order to shew that it was formed by the same hand that constructed our world, teeming with living beings. Standing on the summit of a lunar mountain, and surveying the lifeless waste around, we can have no difficulty in tracing the omnipotence and Divine wisdom that so marvellously moulded this world of ours as a fit abode for all the activities of life. We find the same great law3 that have sway upon our globe. Gravitation reigns there as well as here. The forces that have upheaved the crust of the moon, and moulded it into such strange forms, obeyed similar laws. The configuration of its surface bears a striking resemblance to the diversities on that of the earth. There are differences, but differences that consist with the same type. The solitary peaks, the mountain ranges, the circular craters have their own distinctive characters,曜ust as the scenery of one part of the earth's surface differs from that of another; but yet there is one general plan assimilating them to the analogous terrestrial forms. It is this that gives so great a charm to the contemplation of the lunar surface. The pleasure of travel consists very much in the discovery, in foreign countries, of likeness to our manners and customs, arts and institutions, underlying much apparent and often startling dissimilarity; and when we travel beyond the limits of our own orb, and alight upon this strange island floating in space, we are startled to find it so strange, and yet so like the world that we left behind.

This pleasing similarity may be felt, and the hand of the one omnipotent Architect may be recognised, though we do not find the moon provided with inhabitants. Still it would, no doubt, lend an additional charm, if we had any plausible ground for entertaining such a belief. As soon as the telescope unveiled a world so like our own in its general aspect, the popular imagination peopled it with living forms, and astronomers strove with one another to gratify the popular wish. In the dark surface, active volcanoes were discovered. The flames were seen to burst forth with great vehemence, and then slowly expire, shewing that there was air to sustain the combustion. Planets and fixed stars were seen to linger on its edge before I they passed behind its disc, just as they ought to do if there were an atmosphere. All these observations are now discredited; and the inexorable decision of scientific research is, that there is no valid argument for the existence of an atmosphere. Not long ago, an admirable test was afforded by the occultation of Jupiter, and every astronomer was on the alert to discover the result. The figure of the planet ought to be distorted by the atmosphere, if there was really one, and many eyes were strained to detect the distortion. The result was a strange one. Many saw the exact appearance that ought to be presented; the disc of Jupiter was changed just as theory required. Others again saw no distortion; the disc presented its natural form, and gave no indication of a refracting medium. What deduction are we to draw from such conflicting testimony? Where does the truth lie? The observers were all equally veracious, and they all appealed to the testimony of the senses. Which testimony are we to receive? Or must we hold that the evidence of the one side neutralises that of the other] The objective facts were undoubtedly the same to all; but a curious subjective law of our nature extricates us from the dilemma. The law is that of expectant attention, which explains so many of the facts of mesmerism. When the mind is possessed of some dominant idea, and when, in accordance with it, we have a strong expectation of some event, the senses, in these circumstances, become to a certain extent the sport of our subjective feelings. Taking this fact in our nature into account, and also the well-known character of the observers, the conclusion is, that the distortion of the disc of Jupiter was not real,葉hat it resulted merely from the excited state of the observers' feelings at the moment. Their foregone conclusion overpowered the legitimate testimony of sense. The testimony of the most competent writers was all against the existence of an atmosphere.

The advocates of a plurality of worlds have either abandoned the case of the moon as not one in point, being only a satellite, or resorted to strained hypotheses ; such as, that there may be an atmosphere at the bottom of the valleys, or that the moon must necessarily have appropriated the matter of the tails of comets, and of the zodiacal light. A recent discovery has, however, been made, which entirely changes the aspect of things. In all previous speculations, astronomers have gone on the supposition that what held in reference to one side of the moon, would equally hold in reference to the other. The discovery in question shews that it is by no means a legitimate supposition, and that the non-existence of an atmosphere in the visible side does not at all imply that the other is equally destitute of one.

The moon constantly turns the same side to us. She does, indeed, as if to tantalise us, shew a email portion of the other side. She turns round at one time the western edge, so as to shew us a few more mountains and craters, and then at another the eastern; but it is only a few degrees that she thus reveals. It is by this libration, as we have seen, that we are able to take stereoscopic pictures of her disc. She turns constantly the same side to us, from the simple circumstance, that she rotates once upon her axis, in the time that she performs a revolution round the earth. It at first sight appears like a contradiction, to say that she turns round upon her axis, and yet that she never shews us but one hemisphere. Does not rotation consist in turning round to us all sides in succession? This has always been a puzzle in astronomy, though only very elementary knowledge is sufficient to solve it. Even the acute metaphysician Hegel could not understand how she should rotate, and he proves, from the fundamental principles of his philosophy, that she cannot rotate. The perplexity arises from the position we occupy. If we were without, instead of within the circle she describes in the heavens, there could be no misconception. The inhabitants of the other planets see her turn in succession all parts of her circumference to them. In the course of twenty-eight days they can scrutinise every part of her surface. This arises from the same reason, that a person, in the centre of a circus, sees only one side of the horse galloping round the circumference, while the spectators beyond see both sides in succession.

Until lately, no conjecture could be formed of the state of things on the other side of the moon. It was regarded as one of those inscrutable mysteries which it would be folly to attempt to unveil. Human genius has triumphed over the difficulty, and has thrown a marvellous light on that which has hitherto been involved in deepest darkness. And, in such cases, one feels at a loss which to admire most葉he wonders of God's works, or the genius with which He has endowed man to explore these works, It is to M. Hausen, a distinguished Continental astronomer, that the credit of the discovery is due. Mr Airy, the Astronomer-Royal, supplied him, no doubt, with the data, but the merit of the solution was all his own. The Astronomer-Royal has, as it were, dug up from gome Assyrian mound, a brick with mystic cuneiform characters, and M. Hausen has supplied the key to the interpretation. The moon is so eagerly scrutinised at Greenwich, that any deviation from the prescribed path is soon detected. M. Hausen had already, on more than one occasion, vindicated the law of gravitation, by reducing unexplained lunar irregularities to its dominion. When again applied to, he set to work to discover the cause of the anomaly. The deviation was slight, but if the moon does not keep time to a very second, some explanation is required; and, on this, as on all former occasions, M. Hausen was triumphant. He has given a most marvellous solution, but one in which all astronomers have acquiesced.

The scientific statement of the solution is, that the moon's centre of gravity and her centre of figure are not coincident, the one being distant about eight geographical miles from the other. Most momentous results flow from this. The one hemisphere must be lighter than the other. This, indeed, is but another way of stating the discovery. The sphere of the moon may be regarded as made up of a light half and a heavy one葉he lighter being always turned towards the earth.

But how could such a strange discovery be made? It would not be easy to give a popular explanation of the mathematical process by which M. Hausen arrived at this result, but there is no difficulty in understanding the general principles on which it is founded. In discharging a ball from a gun, calculation can predict the trajectory it will describe. But if the ball is not equally dense on opposite sides, it will not pursue the same path it would do if homogeneous. Let us suppose that while the ball is perfectly spherical, one half is iron and the other cork, the curve described will be different, both in range and form, from that which would be described by a ball equally dense throughout. Balls have been, indeed, purposely so cast, to increase the range葉he sphere being cast hollow, but having one side thicker than the other. Given the difference of density, the curve can be laid down, and given the curve, the difference of density can be determined. This last case is that of the moon. It differs in no respect from a ball discharged from a gun, and, in examining the curve it describes, the conclusion is, that while she is quite or nearly spherical, the hemisphere turned towards us is lighter than the opposite one.

But how does this tell on the question of inhabitants? The application is very direct and startling. Supposing the sphere of the moon originally covered with water, and enveloped in an atmosphere, both water and air would flow to the heavier side, and leave the lighter side destitute of either, just as water and air would leave the summits of mountains, and gravitate towards the valleys. They seek the lowest level, or, in other words, the point least distant from the centre of gravity.

In the case of the moon, the side turned to us is virtually a mountain twenty-nine miles high, and the opposite Bide the corresponding valley. The conclusion is, that though the near hemisphere is a lifeless desert, having neither water nor air to sustain life, the hidden hemisphere may have a teeming population, rejoicing in all the comforts and amenities of life. The imagination is set free to picture broad oceans, bearing on their bosom the commerce of this new world, rivers fertilising the valleys through which they flow, a luxuriant vegetation, and buildings of colossal size.

This, however, only increases the mystery, and the longing to see further round the edge of the moon. If there was mystery before when life was not dreamt of, how much is that mystery increased, when we now know that there may be life葉hat there may be another world the counterpart of our own ! Everything on this side of the moon is fixed in the rigidity of death. No movement is observed indicating life or action. How different would be the other side were we only permitted to obtain a glimpse! Its ever-changing atmosphere would be a source of continual interest; we could study its weather as easily as we could our own. And, if the atmosphere were not too dense, we could watch the progress of agriculture, and the growth of cities. If it is a world of strife, we could distinguish on the battle-field the colour of the uniforms of the opposing masses. All this could be accomplished by our present optical means; and, as our powers of vision increased, we could descend to the minuter details of life. We could readily conceive a code of signals by which telegraphic communication could be carried on. The moon, however, sternly withholds from us her great secret, and for ever turns from us her hidden hemisphere.

Granting that the other side of the moon is peopled, can our world be ever known to the inhabitants, seeing that only the lighter side is turned toward us? It is plain that the inhabitants, if they keep to their own side, can never get a glimpse of our earth. If there be an atmosphere, it is probable that it may extend a small way within the border of the opposite side, though in a rarefied form. We can then conceive the intrepid lunar inhabitants venturing as far as they can breathe within the barren hemisphere; just like adventurous travellers on our globe scaling lofty mountains to obtain an extended view of the landscape. What an astonishing spectacle must burst upon the view of the lunar tourist as soon as he fairly gets within the new hemisphere! The traveller who has spent the night on the summit of the Rigi, to watch the rising of the sun over the snow-clad ranges of the Ober-land Alps, feels rewarded for all his toil by the glorious spectacle. The visitor of the southern hemisphere, when he first beholds the southern cross and the Magellanic clouds, experiences no ordinary delight at having a new portion of God's universe ushered into view. But these illustrations can but imperfectly enable us to realise the case of the lunar traveller, when he first beholds the earth. He will see an immense blue orb hung up, immovably fixed in the heavens. It will appear to him fourteen times larger than the moon appears to us. The sun will be seen, as in the other lunar hemisphere, to rise in one horizon, and in fourteen days set in the opposite, but the earth never moves. The stars at midday, as well as at midnight, will appear to pass behind its disc, while it maintains the same position. But though immovably fixed in the heavens, wondrous activities will be discovered. It will exhibit in twenty-eight days all the phases of the moon溶ow a thin crescent, then a full orb. Its rapid rotation will also be a most notable object, for in so large an orb the twenty-four hours' period will be most marked. And then the blue atmosphere will be undergoing incessant changes. Belts, corresponding to the trade-winds, will be seen, and throughout the whole extent, the varying climates of the world will be observable. Though objects on the surface of our earth will be but dimly descried, still our seas, continents, and mountain-ranges may be distinguished. What a tale of wonder will the traveller have to tell, when, after his perilous adventures, he returns to the bosom of his family!

It is obvious, that the results of M. Hausen furnish no positive evidence for the existence of lunar inhabitants. It is valuable to the advocate of a plurality of worlds, only in as far as it enables him to rebut the argument of his antagonist when he points to the moon as a proof that his speculations are only a dream. He can now maintain, that if we knew all, we would find that the moon is not destitute of life.

While we write, word is brought of the discovery of a new planet, and a new difficulty for the advocate of planetary inhabitants. Strange, that with so many professional eyes gazing day after day at the spots on the sun, it should be left to a provincial doctor in France, with the rudest instruments, to make the discovery of the little black pellet-like spot, which, by its form and rapid motion, indicated the transit of a new planet within the orbit of Mercury. The honour, after all, does not fall to the man of keen eyes, who detected this spot accidentally, but to the master-mind, who, by a finer sense, detected its existence months before the results of observation were made known. Leverrier, in this case, as in that of the planet Neptune, was the intellectual seer.

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