All Around the Moon
Page 11
CHAPTER X.
THE OBSERVERS OF THE MOON.
Barbican's happy conjecture had probably hit the nail on the head. Thedivergency even of a second may amount to millions of miles if you onlyhave your lines long enough. The Projectile had certainly gone off itsdirect course; whatever the cause, the fact was undoubted. It was agreat pity. The daring attempt must end in a failure due altogether to afortuitous accident, against which no human foresight could havepossibly taken precaution. Unless in case of the occurrence of someother most improbable accident, reaching the Moon was evidently nowimpossible. To failure, therefore, our travellers had to make up theirminds.
But was nothing to be gained by the trip? Though missing actual contactwith the Moon, might they not pass near enough to solve several problemsin physics and geology over which scientists had been for a long timepuzzling their brains in vain? Even this would be some compensation forall their trouble, courage, and intelligence. As to what was to be theirown fate, to what doom were themselves to be reserved--they neverappeared to think of such a thing. They knew very well that in the midstof those infinite solitudes they should soon find themselves withoutair. The slight supply that kept them from smothering could notpossibly last more than five or six days longer. Five or six days! Whatof that? _Quand meme_! as Ardan often exclaimed. Five or six days werecenturies to our bold adventurers! At present every second was a year inevents, and infinitely too precious to be squandered away in merepreparations for possible contingencies. The Moon could never bereached, but was it not possible that her surface could be carefullyobserved? This they set themselves at once to find out.
The distance now separating them from our Satellite they estimated atabout 400 miles. Therefore relatively to their power of discovering thedetails of her disc, they were still farther off from the Moon than someof our modern astronomers are to-day, when provided with their powerfultelescopes.
We know, for example, that Lord Rosse's great telescope at Parsonstown,possessing a power of magnifying 6000 times, brings the Moon to within40 miles of us; not to speak of Barbican's great telescope on the summitof Long's Peak, by which the Moon, magnified 48,000 times, was broughtwithin 5 miles of the Earth, where it therefore could reveal withsufficient distinctness every object above 40 feet in diameter.
Therefore our adventurers, though at such a comparatively smalldistance, could not make out the topographical details of the Moon withany satisfaction by their unaided vision. The eye indeed could easilyenough catch the rugged outline of these vast depressions improperlycalled "Seas," but it could do very little more. Its powers ofadjustability seemed to fail before the strange and bewildering scene.The prominence of the mountains vanished, not only through theforeshortening, but also in the dazzling radiation produced by thedirect reflection of the solar rays. After a short time therefore,completely foiled by the blinding glare, the eye turned itselfunwillingly away, as if from a furnace of molten silver.
The spherical surface, however, had long since begun to reveal itsconvexity. The Moon was gradually assuming the appearance of a giganticegg with the smaller end turned towards the Earth. In the earlier daysof her formation, while still in a state of mobility, she had beenprobably a perfect sphere in shape, but, under the influence ofterrestrial gravity operating for uncounted ages, she was drawn at lastso much towards the centre of attraction as to resemble somewhat aprolate spheriod. By becoming a satellite, she had lost the nativeperfect regularity of her outline; her centre of gravity had shiftedfrom her real centre; and as a result of this arrangement, somescientists have drawn the conclusion that the Moon's air and water havebeen attracted to that portion of her surface which is always invisibleto the inhabitants of the Earth.
The convexity of her outline, this bulging prominence of her surface,however, did not last long. The travellers were getting too near tonotice it. They were beginning to survey the Moon as balloonists surveythe Earth. The Projectile was now moving with great rapidity--withnothing like its initial velocity, but still eight or nine times fasterthan an express train. Its line of movement, however, being obliqueinstead of direct, was so deceptive as to induce Ardan to flatterhimself that they might still reach the lunar surface. He could neverpersuade himself to believe that they should get so near their aim andstill miss it. No; nothing might, could, would or should induce him tobelieve it, he repeated again and again. But Barbican's pitiless logicleft him no reply.
"No, dear friend, no. We can reach the Moon only by a fall, and we don'tfall. Centripetal force keeps us at least for a while under the lunarinfluence, but centrifugal force drives us away irresistibly."
These words were uttered in a tone that killed Ardan's last and fondesthope.
* * * * *
The portion of the Moon they were now approaching was her northernhemisphere, found usually in the lower part of lunar maps. The lens of atelescope, as is well known, gives only the inverted image of theobject; therefore, when an upright image is required, an additionalglass must be used. But as every additional glass is an additionalobstruction to the light, the object glass of a Lunar telescope isemployed without a corrector; light is thereby saved, and in viewing theMoon, as in viewing a map, it evidently makes very little differencewhether we see her inverted or not. Maps of the Moon therefore, beingdrawn from the image formed by the telescope, show the north in thelower part, and _vice versa_. Of this kind was the _MappaSelenographica_, by Beer and Maedler, so often previously alluded to andnow carefully consulted by Barbican. The northern hemisphere, towardswhich they were now rapidly approaching, presented a strong contrastwith the southern, by its vast plains and great depressions, checkeredhere and there by very remarkable isolated mountains.[A]
At midnight the Moon was full. This was the precise moment at which thetravellers would have landed had not that unlucky bolide drawn them offthe track. The Moon was therefore strictly up to time, arriving at theinstant rigidly determined by the Cambridge Observatory. She occupiedthe exact point, to a mathematical nicety, where our 28th parallelcrossed the perigee. An observer posted in the bottom of the Columbiadat Stony Hill, would have found himself at this moment precisely underthe Moon. The axis of the enormous gun, continued upwards vertically,would have struck the orb of night exactly in her centre.
It is hardly necessary to tell our readers that, during this memorablenight of the 5th and 6th of December, the travellers had no desire toclose their eyes. Could they do so, even if they had desired? No! Alltheir faculties, thoughts, and desires, were concentrated in one singleword: "Look!" Representatives of the Earth, and of all humanity past andpresent, they felt that it was with their eyes that the race of mancontemplated the lunar regions and penetrated the secrets of oursatellite! A certain indescribable emotion therefore, combined with anundefined sense of responsibility, held possession of their hearts, asthey moved silently from window to window.
Their observations, recorded by Barbican, were vigorously remade,revised, and re-determined, by the others. To make them, they hadtelescopes which they now began to employ with great advantage. Toregulate and investigate them, they had the best maps of the day.
Whilst occupied in this silent work, they could not help throwing ashort retrospective glance on the former Observers of the Moon.
The first of these was Galileo. His slight telescope magnified onlythirty times, still, in the spots flecking the lunar surface, like theeyes checkering a peacock's tail, he was the first to discover mountainsand even to measure their heights. These, considering the difficultiesunder which he labored, were wonderfully accurate, but unfortunately hemade no map embodying his observations.
A few years afterwards, Hevel of Dantzic, (1611-1688) a Polishastronomer--more generally known as Hevelius, his works being allwritten in Latin--undertook to correct Galileo's measurements. But ashis method could be strictly accurate only twice a month--the periods ofthe first and second quadratures--his rectifications could be hardlycalled successful.
Still it is to
the labors of this eminent astronomer, carried onuninterruptedly for fifty years in his own observatory, that we owe thefirst map of the Moon. It was published in 1647 under the name of_Selenographia_. He represented the circular mountains by open spotssomewhat round in shape, and by shaded figures he indicated the vastplains, or, as he called them, the _seas_, that occupied so much of hersurface. These he designated by names taken from our Earth. His mapshows you a _Mount Sinai_ the midst of an _Arabia_, an _AEtna_ in thecentre of a _Sicily_, _Alps_, _Apennines_, _Carpathians_, a_Mediterranean_, a _Palus Maeolis_, a _Pontus Euxinus_, and a _CaspianSea_. But these names seem to have been given capriciously and atrandom, for they never recall any resemblance existing betweenthemselves and their namesakes on our globe. In the wide open spot, forinstance, connected on the south with vast continents and terminating ina point, it would be no easy matter to recognize the reversed image ofthe _Indian Peninsula_, the _Bay of Bengal_, and _Cochin China_.Naturally, therefore, these names were nearly all soon dropped; butanother system of nomenclature, proposed by an astronomer betteracquainted with the human heart, met with a success that has lasted tothe present day.
This was Father Riccioli, a Jesuit, and (1598-1671) a contemporary ofHevelius. In his _Astronomia Reformata_, (1665), he published a roughand incorrect map of the Moon, compiled from observations made byGrimaldi of Ferrara; but in designating the mountains, he named themafter eminent astronomers, and this idea of his has been carefullycarried out by map makers of later times.
A third map of the Moon was published at Rome in 1666 by DominicoCassini of Nice (1625-1712), the famous discoverer of Saturn'ssatellites. Though somewhat incorrect regarding measurements, it wassuperior to Riccioli's in execution, and for a long time it wasconsidered a standard work. Copies of this map are still to be found,but Cassini's original copper-plate, preserved for a long time at the_Imprimerie Royale_ in Paris, was at last sold to a brazier, by no lessa personage than the Director of the establishment himself, who,according to Arago, wanted to get rid of what he considered uselesslumber!
La Hire (1640-1718), professor of astronomy in the _College de France_,and an accomplished draughtsman, drew a map of the Moon which wasthirteen feet in diameter. This map could be seen long afterwards in thelibrary of St. Genevieve, Paris, but it was never engraved.
About 1760, Mayer, a famous German astronomer and the director of theobservatory of Goettingen, began the publication of a magnificent map ofthe Moon, drawn after lunar measurements all rigorously verified byhimself. Unfortunately his death in 1762 interrupted a work which wouldhave surpassed in accuracy every previous effort of the kind.
Next appears Schroeter of Erfurt (1745-1816), a fine observer (he firstdiscovered the Lunar _Rills_), but a poor draughtsman: his maps aretherefore of little value. Lohrman of Dresden published in 1838 anexcellent map of the Moon, 15 inches in diameter, accompanied bydescriptive text and several charts of particular portions on a largerscale.
But this and all other maps were thrown completely into the shade byBeer and Maedler's famous _Mappa Selenographica_, so often alluded to inthe course of this work. This map, projected orthographically--that is,one in which all the rays proceeding from the surface to the eye aresupposed to be parallel to each other--gives a reproduction of the lunardisc exactly as it appears. The representation of the mountains andplains is therefore correct only in the central portion; elsewhere,north, south, east, or west, the features, being foreshortened, arecrowded together, and cannot be compared in measurement with those inthe centre. It is more than three feet square; for convenient referenceit is divided into four parts, each having a very full index; in short,this map is in all respects a master piece of lunar cartography.[B]
After Beer and Maedler, we should allude to Julius Schmitt's (of Athens)excellent selenographic reliefs: to Doctor Draper's, and to FatherSecchi's successful application of photography to lunar representation;to De La Rue's (of London) magnificent stereographs of the Moon, to behad at every optician's; to the clear and correct map prepared byLecouturier and Chapuis in 1860; to the many beautiful pictures of theMoon in various phases of illumination obtained by the Messrs. Bond ofHarvard University; to Rutherford's (of New York) unparalleled lunarphotographs; and finally to Nasmyth and Carpenter's wonderful work onthe Moon, illustrated by photographs of her surface in detail, preparedfrom models at which they had been laboring for more than a quarter ofthe century.
Of all these maps, pictures, and projections, Barbican had providedhimself with only two--Beer and Maedler's in German, and Lecouturier andChapuis' in French. These he considered quite sufficient for allpurposes, and certainly they considerably simplified his labors as anobserver.
His best optical instruments were several excellent marine telescopes,manufactured especially under his direction. Magnifying the object ahundred times, on the surface of the Earth they would have brought theMoon to within a distance of somewhat less than 2400 miles. But at thepoint to which our travellers had arrived towards three o'clock in themorning, and which could hardly be more than 12 or 1300 miles from theMoon, these telescopes, ranging through a medium disturbed by noatmosphere, easily brought the lunar surface to within less than 13miles' distance from the eyes of our adventurers.
Therefore they should now see objects in the Moon as clearly as peoplecan see the opposite bank of a river that is about 12 miles wide.
[Footnote A: In our Map of the Moon, prepared expressly for this work,we have so far improved on Beer and Maedler as to give her surface as itappears to the naked eye: that is, the north is in the north; only wemust always remember that the west is and must be on the _right hand_.]
[Footnote B: In our Map the _Mappa Selenographica_ is copied as closelyand as fully as is necessary for understanding the details of the story.For further information the reader is referred to Nasmyth's latemagnificent work: the MOON.]