A Bird's Eye View Of The Lunar Mountains
:
All Around The Moon
I am rather inclined to believe myself that not one word of Ardan's
rhapsody had been ever heard by Barbican or M'Nicholl. Long before he
had spoken his last words, they had once more become mute as statues,
and now were both eagerly watching, pencil in hand, spyglass to eye, the
northern lunar hemisphere towards which they were rapidly but indirectly
approaching. They had fully made up their minds by this time that they
>
were leaving far behind them the central point which they would have
probably reached half an hour ago if they had not been shunted off their
course by that inopportune bolide.
About half past twelve o'clock, Barbican broke the dead silence by
saying that after a careful calculation they were now only about 875
miles from the Moon's surface, a distance two hundred miles less in
length than the lunar radius, and which was still to be diminished as
they advanced further north. They were at that moment ten degrees north
of the equator, almost directly over the ridge lying between the Mare
Serenitatis and the Mare Tranquillitatis. From this latitude all the
way up to the north pole the travellers enjoyed a most satisfactory view
of the Moon in all directions and under the most favorable conditions.
By means of their spyglasses, magnifying a hundred times, they cut down
this distance of 875 miles to about 9. The great telescope of the Rocky
Mountains, by its enormous magnifying power of 48,000, brought the Moon,
it is true, within a distance of 5 miles, or nearly twice as near; but
this advantage of nearness was considerably more than counterbalanced by
a want of clearness, resulting from the haziness and refractiveness of
the terrestrial atmosphere, not to mention those fatal defects in the
reflector that the art of man has not yet succeeded in remedying.
Accordingly, our travellers, armed with excellent telescopes--of just
power enough to be no injury to clearness,--and posted on unequalled
vantage ground, began already to distinguish certain details that had
probably never been noticed before by terrestrial observers. Even Ardan,
by this time quite recovered from his fit of sentiment and probably
infected a little by the scientific enthusiasm of his companions, began
to observe and note and observe and note, alternately, with all the
sangfroid of a veteran astronomer.
"Friends," said Barbican, again interrupting a silence that had lasted
perhaps ten minutes, "whither we are going I can't say; if we shall ever
revisit the Earth, I can't tell. Still, it is our duty so to act in all
respects as if these labors of ours were one day to be of service to our
fellow-creatures. Let us keep our souls free from every distraction. We
are now astronomers. We see now what no mortal eye has ever gazed on
before. This Projectile is simply a work room of the great Cambridge
Observatory lifted into space. Let us take observations!"
With these words, he set to work with a renewed ardor, in which his
companions fully participated. The consequence was that they soon had
several of the outline maps covered with the best sketches they could
make of the Moon's various aspects thus presented under such favorable
circumstances. They could now remark not only that they were passing the
tenth degree of north latitude, but that the Projectile followed almost
directly the twentieth degree of east longitude.
"One thing always puzzled me when examining maps of the Moon," observed
Ardan, "and I can't say that I see it yet as clearly as if I had thought
over the matter. It is this. I could understand, when looking through a
lens at an object, why we get only its reversed image--a simple law of
optics explains that. Therefore, in a map of the Moon, as the bottom
means the north and the top the south, why does not the right mean the
west and the left the east? I suppose I could have made this out by a
little thought, but thinking, that is reflection, not being my forte, it
is the last thing I ever care to do. Barbican, throw me a word or two on
the subject."
"I can see what troubles you," answered Barbican, "but I can also see
that one moment's reflection would have put an end to your perplexity.
On ordinary maps of the Earth's surface when the north is the top, the
right hand must be the east, the left hand the west, and so on. That is
simply because we look down from above. And such a map seen through
a lens will appear reversed in all respects. But in looking at the Moon,
that is up from down, we change our position so far that our right
hand points west and our left east. Consequently, in our reversed map,
though the north becomes south, the right remains east, and--"
"Enough said! I see it at a glance! Thank you, Barbican. Why did not
they make you a professor of astronomy? Your hint will save me a world
of trouble."[C]
Aided by the Mappa Selenographica, the travellers could easily
recognize the different portions of the Moon over which they were now
moving. An occasional glance at our reduction of this map, given as a
frontispiece, will enable the gentle reader to follow the travellers on
the line in which they moved and to understand the remarks and
observations in which they occasionally indulged.
"Where are we now?" asked Ardan.
"Over the northern shores of the Mare Nubium," replied Barbican. "But
we are still too far off to see with any certainty what they are like.
What is the Mare itself? A sea, according to the early astronomers? a
plain of solid sand, according to later authority? or an immense forest,
according to De la Rue of London, so far the Moon's most successful
photographer? This gentleman's authority, Ardan, would have given you
decided support in your famous dispute with the Captain at the meeting
near Tampa, for he says very decidedly that the Moon has an atmosphere,
very low to be sure but very dense. This, however, we must find out for
ourselves; and in the meantime let us affirm nothing until we have good
grounds for positive assertion."
Mare Nubium, though not very clearly outlined on the maps, is easily
recognized by lying directly east of the regions about the centre. It
would appear as if this vast plain were sprinkled with immense lava
blocks shot forth from the great volcanoes on the right, Ptolemaeus,
Alphonse, Alpetragius and Arzachel. But the Projectile advanced so
rapidly that these mountains soon disappeared, and the travellers were
not long before they could distinguish the great peaks that closed the
"Sea" on its northern boundary. Here a radiating mountain showed a
summit so dazzling with the reflection of the solar rays that Ardan
could not help crying out:
"It looks like one of the carbon points of an electric light projected
on a screen! What do you call it, Barbican?"
"Copernicus," replied the President. "Let us examine old
Copernicus!"
This grand crater is deservedly considered one of the greatest of the
lunar wonders. It lifts its giant ramparts to upwards of 12,000 feet
above the level of the lunar surface. Being quite visible from the Earth
and well situated for observation, it is a favorite object for
astronomical study; this is particularly the case during the phase
existing between Last Quarter and the New Moon, when its vast shadows,
projected boldly from the east towards the west, allow its prodigious
dimensions to be measured.
After Tycho, which is situated in the southern hemisphere,
Copernicus forms the most important radiating mountain in the lunar
disc. It looms up, single and isolated, like a gigantic light-house, on
the peninsula separating Mare Nubium from Oceanus Procellarum on one
side and from Mare Imbrium on the other; thus illuminating with its
splendid radiation three "Seas" at a time. The wonderful complexity of
its bright streaks diverging on all sides from its centre presented a
scene alike splendid and unique. These streaks, the travellers thought,
could be traced further north than in any other direction: they fancied
they could detect them even in the Mare Imbrium, but this of course
might be owing to the point from which they made their observations. At
one o'clock in the morning, the Projectile, flying through space, was
exactly over this magnificent mountain.
In spite of the brilliant sunlight that was blazing around them, the
travellers could easily recognize the peculiar features of Copernicus.
It belongs to those ring mountains of the first class called Circuses.
Like Kepler and Aristarchus, who rule over Oceanus Procellarum,
Copernicus, when viewed through our telescopes, sometimes glistens so
brightly through the ashy light of the Moon that it has been frequently
taken for a volcano in full activity. Whatever it may have been once,
however, it is certainly nothing more now than, like all the other
mountains on the visible side of the Moon, an extinct volcano, only with
a crater of such exceeding grandeur and sublimity as to throw utterly
into the shade everything like it on our Earth. The crater of Etna is at
most little more than a mile across. The crater of Copernicus has a
diameter of at least 50 miles. Within it, the travellers could easily
discover by their glasses an immense number of terraced ridges, probably
landslips, alternating with stratifications resulting from successive
eruptions. Here and there, but particularly in the southern side, they
caught glimpses of shadows of such intense blackness, projected across
the plateau and lying there like pitch spots, that they could not tell
them from yawning chasms of incalculable depth. Outside the crater the
shadows were almost as deep, whilst on the plains all around,
particularly in the west, so many small craters could be detected that
the eye in vain attempted to count them.
"Many circular mountains of this kind," observed Barbican, "can be seen
on the lunar surface, but Copernicus, though not one of the greatest,
is one of the most remarkable on account of those diverging streaks of
bright light that you see radiating from its summit. By looking
steadily into its crater, you can see more cones than mortal eye ever
lit on before. They are so numerous as to render the interior plateau
quite rugged, and were formerly so many openings giving vent to fire and
volcanic matter. A curious and very common arrangement of this internal
plateau of lunar craters is its lying at a lower level than the external
plains, quite the contrary to a terrestrial crater, which generally has
its bottom much higher than the level of the surrounding country. It
follows therefore that the deep lying curve of the bottom of these ring
mountains would give a sphere with a diameter somewhat smaller than the
Moon's."
"What can be the cause of this peculiarity?" asked M'Nicholl.
"I can't tell;" answered Barbican, "but, as a conjecture, I should say
that it is probably to the comparatively smaller area of the Moon and
the more violent character of her volcanic action that the extremely
rugged character of her surface is mainly due."
"Why, it's the Campi Phlegraei or the Fire Fields of Naples over
again!" cried Ardan suddenly. "There's Monte Barbaro, there's the
Solfatara, there is the crater of Astroni, and there is the Monte
Nuovo, as plain as the hand on my body!"
"The great resemblance between the region you speak of and the general
surface of the Moon has been often remarked;" observed Barbican, "but
it is even still more striking in the neighborhood of Theophilus on
the borders of Mare Nectaris."
"That's Mare Nectaris, the gray spot over there on the southwest,
isn't it?" asked M'Nicholl; "is there any likelihood of our getting a
better view of it?"
"Not the slightest," answered Barbican, "unless we go round the Moon and
return this way, like a satellite describing its orbit."
By this time they had arrived at a point vertical to the mountain
centre. Copernicus's vast ramparts formed a perfect circle or rather a
pair of concentric circles. All around the mountain extended a dark
grayish plain of savage aspect, on which the peak shadows projected
themselves in sharp relief. In the gloomy bottom of the crater, whose
dimensions are vast enough to swallow Mont Blanc body and bones, could
be distinguished a magnificent group of cones, at least half a mile in
height and glittering like piles of crystal. Towards the north several
breaches could be seen in the ramparts, due probably to a caving in of
immense masses accumulated on the summit of the precipitous walls.
As already observed, the surrounding plains were dotted with numberless
craters mostly of small dimensions, except Gay Lussac on the north,
whose crater was about 12 miles in diameter. Towards the southwest and
the immediate east, the plain appeared to be very flat, no protuberance,
no prominence of any kind lifting itself above the general dead level.
Towards the north, on the contrary, as far as where the peninsula
jutted on Oceanus Procellarum, the plain looked like a sea of lava
wildly lashed for a while by a furious hurricane and then, when its
waves and breakers and driving ridges were at their wildest, suddenly
frozen into solidity. Over this rugged, rumpled, wrinkled surface and in
all directions, ran the wonderful streaks whose radiating point appeared
to be the summit of Copernicus. Many of them appeared to be ten miles
wide and hundreds of miles in length.
The travellers disputed for some time on the origin of these strange
radii, but could hardly be said to have arrived at any conclusion more
satisfactory than that already reached by some terrestrial observers.
To M'Nicholl's question:
"Why can't these streaks be simply prolonged mountain crests reflecting
the sun's rays more vividly by their superior altitude and comparative
smoothness?"
Barbican readily replied:
"These streaks can't be mountain crests, because, if they were, under
certain conditions of solar illumination they should project
shadows--a thing which they have never been known to do under any
circumstances whatever. In fact, it is only during the period of the
full Moon that these streaks are seen at all; as soon as the sun's rays
become oblique, they disappear altogether--a proof that their appearance
is due altogether to peculiar advantages in their surface for the
reflection of light."
"Dear boys, will you allow me to give my little guess on the subject?"
asked Ardan.
His companions were profuse in expressing their desire to hear it.
"Well then," he resumed, "seeing that these bright streaks invariably
start from a certain point to radiate in all directions, why not suppose
them to be streams of lava issuing from the crater and flowing down the
mountain side until they cooled?"
"Such a supposition or something like it has been put forth by
Herschel," replied Barbican; "but your own sense will convince you that
it is quite untenable when you consider that lava, however hot and
liquid it may be at the commencement of its journey, cannot flow on for
hundreds of miles, up hills, across ravines, and over plains, all the
time in streams of almost exactly equal width."
"That theory of yours holds no more water than mine, Ardan," observed
M'Nicholl.
"Correct, Captain," replied the Frenchman; "Barbican has a trick of
knocking the bottom out of every weaker vessel. But let us hear what he
has to say on the subject himself. What is your theory. Barbican?"
"My theory," said Barbican, "is pretty much the same as that lately
presented by an English astronomer, Nasmyth, who has devoted much study
and reflection to lunar matters. Of course, I only formulate my theory,
I don't affirm it. These streaks are cracks, made in the Moon's surface
by cooling or by shrinkage, through which volcanic matter has been
forced up by internal pressure. The sinking ice of a frozen lake, when
meeting with some sharp pointed rock, cracks in a radiating manner:
every one of its fissures then admits the water, which immediately
spreads laterally over the ice pretty much as the lava spreads itself
over the lunar surface. This theory accounts for the radiating nature of
the streaks, their great and nearly equal thickness, their immense
length, their inability to cast a shadow, and their invisibility at any
time except at or near the Full Moon. Still it is nothing but a theory,
and I don't deny that serious objections may be brought against it."
"Do you know, dear boys," cried Ardan, led off as usual by the slightest
fancy, "do you know what I am thinking of when I look down on the great
rugged plains spread out beneath us?"
"I can't say, I'm sure," replied Barbican, somewhat piqued at the little
attention he had secured for his theory.
"Well, what are you thinking of?" asked M'Nicholl.
"Spillikins!" answered Ardan triumphantly.
"Spillikins?" cried his companions, somewhat surprised.
"Yes, Spillikins! These rocks, these blocks, these peaks, these streaks,
these cones, these cracks, these ramparts, these escarpments,--what are
they but a set of spillikins, though I acknowledge on a grand scale? I
wish I had a little hook to pull them one by one!"
"Oh, do be serious, Ardan!" cried Barbican, a little impatiently.
"Certainly," replied Ardan. "Let us be serious, Captain, since
seriousness best befits the subject in hand. What do you think of
another comparison? Does not this plain look like an immense battle
field piled with the bleaching bones of myriads who had slaughtered each
other to a man at the bidding of some mighty Caesar? What do you think
of that lofty comparison, hey?"
"It is quite on a par with the other," muttered Barbican.
"He's hard to please, Captain," continued Ardan, "but let us try him
again! Does not this plain look like--?"
"My worthy friend," interrupted Barbican, quietly, but in a tone to
discourage further discussion, "what you think the plain looks like is
of very slight import, as long as you know no more than a child what it
really is!"
"Bravo, Barbican! well put!" cried the irrepressible Frenchman. "Shall I
ever realize the absurdity of my entering into an argument with a
scientist!"
But this time the Projectile, though advancing northward with a pretty
uniform velocity, had neither gained nor lost in its nearness to the
lunar disc. Each moment altering the character of the fleeting landscape
beneath them, the travellers, as may well be imagined, never thought of
taking an instant's repose. At about half past one, looking to their
right on the west, they saw the summits of another mountain; Barbican,
consulting his map, recognized Eratosthenes.
This was a ring mountain, about 33 miles in diameter, having, like
Copernicus, a crater of immense profundity containing central cones.
Whilst they were directing their glasses towards its gloomy depths,
Barbican mentioned to his friends Kepler's strange idea regarding the
formation of these ring mountains. "They must have been constructed," he
said, "by mortal hands."
"With what object?" asked the Captain.
"A very natural one," answered Barbican. "The Selenites must have
undertaken the immense labor of digging these enormous pits at places of
refuge in which they could protect themselves against the fierce solar
rays that beat against them for 15 days in succession!"
"Not a bad idea, that of the Selenites!" exclaimed Ardan.
"An absurd idea!" cried M'Nicholl. "But probably Kepler never knew the
real dimensions of these craters. Barbican knows the trouble and time
required to dig a well in Stony Hill only nine hundred feet deep. To dig
out a single lunar crater would take hundreds and hundreds of years, and
even then they should be giants who would attempt it!"
"Why so?" asked Ardan. "In the Moon, where gravity is six times less
than on the Earth, the labor of the Selenites can't be compared with
that of men like us."
"But suppose a Selenite to be six times smaller than a man like us!"
urged M'Nicholl.
"And suppose a Selenite never had an existence at all!" interposed
Barbican with his usual success in putting an end to the argument. "But
never mind the Selenites now. Observe Eratosthenes as long as you have
the opportunity."
"Which will not be very long," said M'Nicholl. "He is already sinking
out of view too far to the right to be carefully observed."
"What are those peaks beyond him?" asked Ardan.
"The Apennines," answered Barbican; "and those on the left are the
Carpathians."
"I have seen very few mountain chains or ranges in the Moon," remarked
Ardan, after some minutes' observation.
"Mountains chains are not numerous in the Moon," replied Barbican, "and
in that respect her oreographic system presents a decided contrast with
that of the Earth. With us the ranges are many, the craters few; in the
Moon the ranges are few and the craters innumerable."
Barbican might have spoken of another curious feature regarding the
mountain ranges: namely, that they are chiefly confined to the northern
hemisphere, where the craters are fewest and the "seas" the most
extensive.
For the benefit of those interested, and to be done at once with this
part of the subject, we give in the following little table a list of the
chief lunar mountain chains, with their latitude, and respective
heights in English feet.
Name. Degrees of Latitude. Height.
{ Altai Mountains 17 deg. to 28 13,000ft.
Southern { Cordilleras 10 to 20 12,000
Hemisphere. { Pyrenees 8 to 18 12,000
{ Riphean 5 to 10 2,600
{ Haemus 10 to 20 6,300
{ Carpathian 15 to 19 6,000
{ Apennines 14 to 27 18,000
Northern { Taurus 25 to 34 8,500
Hemisphere. { Hercynian 17 to 29 3,400
{ Caucasus 33 to 40 17,000
{ Alps 42 to 30 10,000
Of these different chains, the most important is that of the
Apennines, about 450 miles long, a length, however, far inferior to
that of many of the great mountain ranges of our globe. They skirt the
western shores of the Mare Imbrium, over which they rise in immense
cliffs, 18 or 20 thousand feet in height, steep as a wall and casting
over the plain intensely black shadows at least 90 miles long. Of Mt.
Huyghens, the highest in the group, the travellers were just barely
able to distinguish the sharp angular summit in the far west. To the
east, however, the Carpathians, extending from the 18th to 30th
degrees of east longitude, lay directly under their eyes and could be
examined in all the peculiarities of their distribution.
Barbican proposed a hypothesis regarding the formation of those
mountains, which his companions thought at least as good as any other.
Looking carefully over the Carpathians and catching occasional
glimpses of semi-circular formations and half domes, he concluded that
the chain must have formerly been a succession of vast craters. Then had
come some mighty internal discharge, or rather the subsidence to which
Mare Imbrium is due, for it immediately broke off or swallowed up one
half of those mountains, leaving the other half steep as a wall on one
side and sloping gently on the other to the level of the surrounding
plains. The Carpathians were therefore pretty nearly in the same
condition as the crater mountains Ptolemy, Alpetragius and
Arzachel would find themselves in, if some terrible cataclysm, by
tearing away their eastern ramparts, had turned them into a chain of
mountains whose towering cliffs would nod threateningly over the western
shores of Mare Nubium. The mean height of the Carpathians is about
6,000 feet, the altitude of certain points in the Pyrenees such as the
Port of Pineda, or Roland's Breach, in the shadow of Mont Perdu.
The northern slopes of the Carpathians sink rapidly towards the shores
of the vast Mare Imbrium.
Towards two o'clock in the morning, Barbican calculated the Projectile
to be on the 20th northern parallel, and therefore almost immediately
over the little ring mountain called Pytheas, about 4600 feet in
height. The distance of the travellers from the Moon at this point
could not be more than about 750 miles, reduced to about 7 by means of
their excellent telescopes.
Mare Imbrium, the Sea of Rains here revealed itself in all its
vastness to the eyes of the travellers, though it must be acknowledged
that the immense depression so called, did not afford them a very clear
idea regarding its exact boundaries. Right ahead of them rose Lambert
about a mile in height; and further on, more to the left, in the
direction of Oceanus Procellarum, Euler revealed itself by its
glittering radiations. This mountain, of about the same height as
Lambert, had been the object of very interesting calculations on the
part of Schroeter of Erfurt. This keen observer, desirous of inquiring
into the probable origin of the lunar mountains, had proposed to himself
the following question: Does the volume of the crater appear to be equal
to that of the surrounding ramparts? His calculations showing him that
this was generally the case, he naturally concluded that these ramparts
must therefore have been the product of a single eruption, for
successive eruptions of volcanic matter would have disturbed this
correlation. Euler alone, he found, to be an exception to this general
law, as the volume of its crater appeared to be twice as great as that
of the mass surrounding it. It must therefore have been formed by
several eruptions in succession, but in that case what had become of the
ejected matter?
Theories of this nature and all manner of scientific questions were, of
course, perfectly permissible to terrestrial astronomers laboring under
the disadvantage of imperfect instruments. But Barbican could not think
of wasting his time in any speculation of the kind, and now, seeing that
his Projectile perceptibly approached the lunar disc, though he
despaired of ever reaching it, he was more sanguine than ever of being
soon able to discover positively and unquestionably some of the secrets
of its formation.
[Footnote C: We must again remind our readers that, in our map, though
every thing is set down as it appears to the eye not as it is reversed
by the telescope, still, for the reason made so clear by Barbican, the
right hand side must be the west and the left the east.]