many selenographers could recall them without referring to a chart. Let
us begin with the greatest of all, Clavius, which, you see, is near the
top of the picture. I think I told you before that Clavius is more than
140 miles across. The great plain within the walls sinks 12,000 feet
below the crest of the irregular ring, but the plateau outside, on the
west, is almost level with the top of the ring. It is difficult to
imagine a more wonderful or imposing spectacle than that which Clavius
would present to a person approaching it from the western side, and
arriving at about the time when this photograph was made, on the top of
the wall. Notice how in one place the summit of a ridge, standing off on
the inner side of the western wall, has come into the sunlight, and
think of the frightful chasm that must yawn between. Clavius is so
enormous that the two crater rings, each with a central mountain
standing on its wall, seem very small in comparison with the giant that
carries them, and yet they are 25 miles in diameter! Stretched out into
a straight line, the tremendous wall of Clavius would form a range of
towering mountains, extending as far as from Buffalo to New York. Look
at the curved row of craters, the smallest larger than any on the earth,
which runs across the interior. In addition to these there are many
smaller craters and mountains standing on the vast sunken plain, some of
them looking like mere pinholes, and yet all of really great size.”
“Truly,” interrupted my listener, “the giantism—I think that is the word
you employ—the giantism of the moon appalls me! How can I ever think,
again, that the so-called great spectacles of nature on the earth are
really great? You have destroyed my sense of proportion. Such immense
things standing on a world so small as the moon—why it seems contrary to
nature’s laws.”
“I have already told you that the very smallness of the moon may be the
underlying cause of the greatness of her surface features. And I may now
add that if your imagined inhabitants ever existed they, too, may have
been affected with ‘giantism.’ A man could be 36 feet tall on the moon
and well proportioned at that, without losing anything in the way of
activity.”
“Indeed! You almost make me hope that there never were such inhabitants,
for what beauty could there be in a human being as tall as a tree?”
“Very little to our eyes, perhaps. You recall the impressions of
Gulliver in the land of the Brobdingnags. However, they are not my
inhabitants but yours, and if the law of gravitation says that they must
have been twelve yards tall, then twelve yards tall they were. Take
comfort, nevertheless, in the reflection that, after all, we cannot
positively assert that gravitation alone governs the size of living
beings on any particular world. We have microscopic creatures as well as
whales and elephants on the earth, and human stature itself is very
variable.”
“Thank you, again. You have saved my lunarians. And now please tell me
what is that frightful black chasm above Clavius?”
“It is a ring plain named Blancanus, 50 miles in diameter, and
exceedingly deep. It is so black and terrible because complete night yet
reigns within it, except on the face of its eastern wall. It is really a
magnificent formation when well lighted, but like so many other great
things it suffers through its nearness to the overmastering Clavius.
When Goliath was in the field his fellow Philistines cut but a sorry
figure. Look at the marvelous region just below Blancanus and imagine
yourself entangled in that labyrinth! You would have but a small chance
for escape, I fancy.”
“I am sure I should never have the heart to even try to get out of it.
One might as well give up at once.”
“Yes, you are probably right. But I will direct you to something not
quite so frightful, although still very formidable in appearance. Still
farther below you observe a huge ring plain whose eastern wall is
brightly illuminated, while nearly all the interior plain, although
comparatively dark in tone, lies in the sunshine. It is Longomontanus. I
pointed it out to you in one of the smaller photographs. Longomontanus
is 90 miles across and 13,000 or 14,000 feet deep, measured from its
loftiest bordering peaks. The very irregular formation below it is
Wilhelm I. It is remarkable for the mountainous character of its
interior.”
“For what William was it named?”
“I do not know. We are now near the southern border of the region that
we inspected in the preceding photograph. In the lower part of this
picture you perceive some of the projecting bays of the _Mare Nubium_,
and you can see again the remarkable cleft of which I spoke. The large
ring near the bottom of the picture is Pitatus with its smaller neighbor
Hesiodus. It is from the eastern side of the latter that the cleft
apparently starts. Pitatus, you see, has a central peak, while Hesiodus,
as if for the sake of contrast, possesses only a central crater pit. The
ravine connecting the two is plainly visible. Toward the east you will
recognize again Cichus, with its crater on the wall and its broad shadow
with a sharp point, while still farther east, on the very edge of night,
yawns Capuanus. The two walled plains above Pitatus are Gauricus on the
left and Wurzelbauer on the right. The hexagonal shape of the former is
very striking. This is a not uncommon phenomenon where the lunar
volcanoes and rings are closely crowded, and it suggests the effect of
mutual compression, like the cells of a honeycomb. Away over in the
northwestern corner is a vast plain marked by a conspicuous crater ring
which bears the startling name of Hell. It borrows its cognomen,
however, from an astronomer, and not, as you might suppose, from Dante’s
‘Inferno.’
“Before quitting this photograph permit me to recall you to the
neighborhood of Tycho and Clavius. To the left of a line joining them
you will perceive a flat, oval plain with a much broken mountain ring.
This is Maginus. Last evening while we were looking at one of the
smaller photographs I pointed it out under a more favorable
illumination, telling you at the same time that it possessed the
peculiarity of almost completely disappearing at Full Moon. Already,
although day has not advanced very far upon it, you observe that it has
become relatively inconspicuous. This is a lesson in the curious effects
of light and shadow in alternately revealing and concealing vast objects
on the moon. You will notice that in many particulars Maginus resembles
a reduced copy of Clavius. But the walls of Clavius are in a
comparatively perfect condition while those of Maginus have apparently
crumbled and fallen, destroyed by forces of whose nature we can only
form guesses. Evidently the destruction has not been wrought, like that
of some of the rings in the _Mare Nubium_, by an inundation of liquid
rock from beneath the crust. It resembles the effects of the
‘weathering’ which gradually brings down the mountains of the earth, but
if such agencies ever acted upon the moon, then it must have had an
atmosphere and an abundance of water. In any event, here before us is
another page of lunar chronology. Maginus is evidently far older than
Clavius; Clavius is older than the craters standing on its own walls.”
We now took up the third of the large photographs representing a part of
the southwestern quarter of the moon, more extraordinary for its
mountains, plateaus, and extinct volcanoes than the famous southwestern
region of the United States.
“Here is something that you will surely recognize without any
assistance,” I said. “In the lower left-hand corner of the picture is
the great three-link chain of crater rings, of which Theophilus is the
principal and most perfect member.”
“Oh, I recall them well,” replied my friend. “And yet they do not appear
to me exactly the same as when I saw them before.”
[Illustration:
THE GREAT SOUTHWEST ON THE MOON.
]
“One reason for that is because this photograph represents them on a
much larger scale, and with infinitely more detail. Another reason is
that now we are looking at them in the lunar afternoon instead of the
lunar morning. We are going to see them represented on a still larger
scale, presently, but there are many things in this picture well worthy
of study. Advancing from the west, the line of night has fallen over the
extreme eastern border of the _Mare Nectaris_, and the shadows thrown by
the setting sun point westward. Observe how beautifully the brightly
illuminated terraces and mighty cliffs of the western wall of Theophilus
contrast with the black shadow that projects over half of the interior
from the sharp verge of the eastern wall. The complicated central
mountain is particularly well shown. The loftiest peak of this mountain
mass, which covers 300 square miles, is 6,000 feet in height. You will
see its shadow reaching the foot of the western wall. Theophilus is 64
miles in diameter, ten miles more than Tycho, and it is deeper than
Tycho, the floor sinking 18,000 feet below the top of the highest point
on the western wall. If it were the focus of a similar ray system it
would deserve to be called the ‘Metropolitan Crater’ rather than Tycho.
Plainly, Theophilus was formed later than its neighbor Cyrillus, because
the southwestern wall of the latter has been destroyed to make room for
the perfect ring of Theophilus.
“The interior of Cyrillus, you will observe, is very different from that
of Theophilus. The floor is more irregular and mountainous. The wall,
also, is much more complex than that of Theophilus. The broken state of
the wall in itself is an indication of the greater age of Cyrillus. On
the south an enormous pass in the wall of Cyrillus leads out upon a
mountain-edged plateau which continues to the wall of the third of the
great rings, Catharina. This formation seems to be of about the same age
as Cyrillus, possibly somewhat older. Its wall is more broken and worn
down, and the northern third of the inclosure is occupied by the wreck
of a large ring. Observe the curious row of relatively small craters,
with low mountain ranges paralleling them, which begins at the
southwestern corner of Cyrillus and runs, with interruptions, for 150
miles or more. South of this is a broad valley with small craters on its
bottom, and then comes an elongated mountainous region with a
conspicuous crater in its center, beyond which appears another valley,
which passes round the east side of Catharina, where it is divided in
the center by a short range of hills. The southeastern side of this
valley is bounded by the grand cliffs of the Altai Mountains, which
continue on until they encounter the eastern wall of the great ring of
Piccolomini, whose interior appears entirely dark in the picture, only a
few peaks on the wall indicating the outlines of the ring. The serrated
shadow of these mountains, thrown westward by the setting sun, forms one
of the most striking features of the photograph. The northeastern end of
the chain also terminates at a smaller ring named Tacitus. You see that
Riccioli was rather cosmopolitan in his tastes, since he has placed the
name of a Roman historian also on the moon. Beginning at a point on the
crest of the Altai range, south of Tacitus, is a very remarkable chain
of small craters, which extends eastward to the southern side of a
beautiful ring plain with a white spot in the center. This ring is named
Abulfeda. The chain of small craters or pits to which I have referred
continues, though much less conspicuous, across the valley that lies
northwest of the Altais. It is a very curious phenomenon, and recalls
the theory advocated by W. K. Gilbert, the American geologist, that the
moon’s craters were formed not by volcanic eruptions but by the impact
of gigantic meteorites falling upon the moon, and originating, perhaps,
in the destruction of a ring which formerly surrounded the earth,
somewhat as the planet Saturn is surrounded by rings of meteoric bodies,
which may eventually be precipitated upon its surface. The moon is more
or less pitted with craterlets in all quarters, but there are places
where they particularly abound. On inspecting this photograph carefully
you will perceive several rows of much larger pits, two or three of them
in the upper half of the picture, and one below the center, crossing the
little chain of pits that I have just mentioned. The linear arrangement
of some of the ring plains is also very striking. In regard to the
theory that the lunar craters were formed by the impact of falling
masses I may mention that two distinguished French students of the moon,
Messrs. Loewy and Puiseux, have lately expressed the opinion that all of
the features of the lunar surface are most readily explicable as the
result of causes similar to those which have produced the topography of
the earth. If that is so there is no need for us to invoke the agency of
meteorites in pitting the surface of the moon. South of the Altai
Mountains you will see a singular collocation of ring plains and craters
which somewhat resemble in their arrangement Theophilus and its
neighbors. First comes a large sunken plain just above the mountains. In
fact the Altai range constitutes the northwestern wall of this
formation, which you may recognize by a conspicuous oval crater near its
upper side. Above this broken ring appear three other smaller ones,
grouped at the corners of a triangle. The one on the right, with a
central pit and a small ring plain on the inside of its western wall, is
called Zagut. Its close neighbor on the west with most of its interior
in shadow, is Lindenau, remarkable for its depth. The most southerly and
largest of the group, with four or five large crater pits forming a
curved row across its interior, is named Rabbi Levi. Starting from the
east side of Rabbi Levi there is a long row of similar craters rather
larger than those in its interior, which runs eastward almost to the
edge of the photograph. North of these, parallel with and, in some
instances, touching the crater pits, is an equally remarkable row of
flat, smooth, walled valleys, which seem to overlap one another on their
western sides, and which increase in size the farther east they go. The
largest of these, with a very irregular wall, and having a smaller ring
with a central peak apparently attached to its northern side, is Gemma
Frisius.”
My friend had listened to me in silence for a long time, following my
finger as it pointed out the various objects on the photograph, but now
she interrupted again: “You were pleased to compliment my memory a
little while ago,” she said, “but do you really think that I can ever
recall all this that you have been saying, with theories about huge
flying stones hitting the moon, and a string of the strangest names that
I have ever heard applied to objects that are no less bizarre?”
“Pardon me,” I replied, “but you will remember more than you think you
will. The very oddity of these Hebraic and Arabic names will serve to
fix them in your memory, so that you will at least recognize them when
you see them again. Those curious objects will also come before your
mind’s eye whenever you think of, or look at, the moon. Trust me when I
tell you that you are forming a better acquaintance with selenography
than you are aware of. As to the theory that I have mentioned, what can
appeal more powerfully to the imagination than the idea of the moon
being bombarded by the fragments of an immense ring falling from the
sky? The fact that men of science have believed such a thing possible
ought to form a strong appeal to your lively fancy. In any case, I am
disposed to be merciless just now, like a man who has found a patient
listener to his hobby, and I am going to trouble you with a few more odd
names and singular facts.”
“Well,” she replied, with a sigh, ending with a smile, “go on. After all
I believe I am really interested.”
“I am sure you are, for who could fail to be interested by things so
remarkable in themselves, and so vastly beyond all human experience, as
those that this photograph shows? We stopped at Gemma Frisius. Let us
use that for a new starting point. A considerable distance south, say
about a hundred miles, is an old friend of ours, Maurolycus. It is the
large ring plain, with another half obliterated, on its southern side,
in the upper part of the picture. Notice the row of wrecked rings,
beginning at a great crater on its northeast wall and running westward.
The broad, flat plain directly east of Maurolycus is Stöfler, whose name
you will also recall. I shall not trouble you with the names of all the
rings south of Stöfler and Maurolycus, but simply ask you to observe
that they form a winding row which leads to a very grand ring almost
entirely buried in night, the inside of its western wall alone being
bright with sunshine. This wall, and some mountain peaks near it,
resemble brilliant islands lying in the edge of the Cimmerian ocean
whose ethereal waves wash the broken coast of the moon. Follow the
ragged sunset line downward, and all along you will see these islands of
light in the darkness; tips of mountains still shining while the sun has
set upon all the valleys around, somewhat as you have seen the snowy top
of Mont Blanc and the pinnacles of its attendant giants glowing after
the shades of night have fallen deep upon Chamounix.
“Look next, if you please, at the right-hand side of the photograph.
Somewhat above the center, three conspicuous dish-shaped ring plains are
seen, two near together, the third farther away toward the left and
downward. The largest of these is Aliacensis, its near neighbor is
Werner, and the third is Apianus. They are from 40 to 50 miles in
diameter. Still lower, and nearer the middle line of the picture, is a
row of four or five ring plains, varying from 30 to 40 miles in
diameter. The uppermost, or most southerly of these is double, or, in
fact, partly triple, for the lower member of the pair has a broken plain
attached to its southeastern side. This one, with a small central peak,
is named Abenezra. Its close neighbor on the southwest is Azophi. You
notice the singularity of the names. The next one below, with a small
crater on its east side, is Geber. Then comes Almamon, and finally,
largest of all, Abulfeda, which I pointed out to you as marking the end
of the curious row of little crater pits, running eastward from the
Altai Mountains. There is just one other formation to which I wish to
call your attention in this remarkable photograph, and then we shall
turn to the next in the series. West of Abenezra and Azophi, about half
way to the Altai Mountains, you will notice a very irregular depression
with three strongly marked craters within it. This bears the name of
Sacrobosco, an old-time astronomer. Its eastern wall with its shadow
looks like an elongated letter W standing on end. Sacrobosco and its
surroundings constitute one of the most intricate regions on the moon,
high plateaus alternating with great sunken valleys, rings, craters, and
crater pits. The wall of Sacrobosco is extremely irregular in height,
shooting up in some places with peaks of 12,000 feet elevation, and
sinking in others almost to the level of the surrounding plateaus.”
We now took up the next photograph representing Theophilus and its
companions on a greatly enlarged scale. My friend uttered a cry of
astonishment upon seeing it.
“Dear me,” she exclaimed, “the moon becomes more terrible every moment!
Positively, I almost shrink from the sight.”
[Illustration:
THE GIANT RING MOUNTAINS, THEOPHILUS AND ITS NEIGHBORS.
]
“Yes,” I assented, “it surely is terrible here. In a little while,
however, I shall show you a lunar scene of surpassing beauty. But study
this spectacle with an inquiring mind and you will find that it, too,
has its attractions. You are now looking upon Theophilus, Cyrillus,
Catharina, and the surrounding region as the astronomer sees them with
the most powerful telescopes. Indeed, with the telescope he sees the
details more sharply than they are visible here, for the best
photographs still lack something in distinctness. The illumination when
this picture was taken was practically the same as in the last that we
examined, but the magnification is much greater. Look, now, at the
central mountain in Theophilus. Its great buttresses cast their shadows
into profound ravines and chasms, imparting to it a most singular
outline. Observe the tooth-shaped shadows of its two principal peaks,
thrown westward across the floor, while the broad shadow of the western
wall emphasizes the immense depth of the depression. The glare of the
afternoon sun on the cliffs of the inner side of the eastern wall is so
brilliant that the details are obscured. But the surface of the moon
outside, particularly toward the north and the west, is beautifully
brought out with all its wonderful modulations and irregularities.
Judging by appearances, those who hold that Theophilus and similar
formations, notwithstanding their enormous magnitude, are really of
volcanic origin, have the strongest reasons for their opinions. Immense
flows of lava seem to have taken place on all sides of the great ring,
entering the _Mare Nectaris_ on the west. Notice the huge mountain fold
which runs from the parallel ridges on the southwestern side of
Theophilus to the crater ring Beaumont, lying west of Catharina.
Observe, also, the complicated form of the wall dividing Theophilus and
Cyrillus. Two deep ravines, shown by the shadows that fill them, cross
one another like the arms of a flat letter X. One of these ravines turns
northward along the wall and re-enters Theophilus, while the other
continues for a long distance within the western side of Cyrillus. I
cannot imagine a more interesting or a more stupendous excursion for a
geologist, a mountaineer, or a seeker after wonderful and sublime
aspects of nature, than a climb around the crest of the wall of
Theophilus—if indeed such a climb can be regarded as humanly possible.
“Now, again, I am reminded of what I once told you about the amazing
contrasts of light and darkness, and of heat and cold, upon the moon.
Suppose yourself standing on the verge of the eastern wall of Theophilus
where the edge seems sharpest, and looking down into the abyss at your
feet. The sun’s rays would be unbearably hot where they touched your
face and hands, but if you let yourself down a little way into the
blackness beneath you would not only pass instantly into night, but you
would shiver and shrink with cold so frightful that no winter experience
that you have ever had could give an idea of its intensity. From that
point of observation you would look across a chasm of inky darkness, 25
miles broad, and see, towering up from the illuminated plain afar off,
with their summits more than two miles below your level, the brilliant
group of the central peaks, while behind them the crest of the western
wall would appear like a bright line on the horizon 60 miles away.
Changing your place to one of the peaks on the dividing wall you would
look down into Theophilus on one side and Cyrillus on the other. Then
upon lifting your eyes to the black, airless sky you would see the stars
sparkling on all hands, and, hanging in the heavens like a portentous,
strangely colored moon many times larger than the disk of the sun, would
appear the mottled orb of the earth. The terrific nature of the scenery
around you, the meeting of day and night at your feet, and the
incredible blending together of their characteristic aspects in the sky
above you, the startling magnitude of the suspended earth—all these
things combined would make you feel as if you were not only in another
world but in another universe.”
“I no longer wish to visit the moon,” interrupted my friend, shaking her
head.
“Not if you were assured of a safe return?”
“No, it would upset my mind. I am certain that I should go crazy in such
a world where everything seems to be topsy-turvy.”