these excessively long days and nights would be very serious to beings
fashioned upon the terrestrial plan. In the practical absence of an
atmosphere the heat of the sun’s rays, pouring down without interruption
and without the intervention of any clouds or vapors for fourteen days
at a time, must be simply overpowering. And then, during the equally
long night that ensues, the radiation into open space must quickly leave
the surface of the moon exposed to the most frightful degree of cold,
comparable with the absolute zero of empty space!”
“But think, what a merciless environment you are picturing for my
inhabitants of the moon. Please do not forget that I insist that their
comfort shall be considered.”
“Oh, as for that, you know you were content a little while ago to
relegate your inhabitants to a remote period in the past, after the
volcanic fury of the lunar world had ceased, and before its present
airless and waterless condition had supervened. Possibly at that time
things were not so uncomfortable for them. They may have had clouds to
temper the sunshine, rains to cool the days and dews the nights, and
shady parks like yours for philosophic and scientific contemplation.”
“Do not forget the poets.”
“Certainly not. But is not the moon herself the very spirit of poetry?
What in nature is more poetical in its suggestions than the moon wading
through fleecy clouds on a serene summer’s night? But pardon me, we are
forgetting my mountains, upon which I insist as strongly as you do upon
your inhabitants. The mountains have this advantage that they are very
real, and no exercise of the imagination is required to bring them
clearly before us. In photograph No. 8 they are all visible. The
Apennines, the greatest of them, start from the eastern end of the _Mare
Serenitatis_, and run in a slightly curved line southeastward, a
distance of about 450 miles. They form the singular ornament which the
Moon Maiden (or shall we now call her Helen of Troy?) wears upon her
forehead. Turn the photograph upside down so that the moon is presented
as the naked eye sees it in the sky, and you will find that, although he
aimed only to be scientifically exact and to exclude everything but the
real facts, Mr. Wallace has produced an excellent picture of this
wonderful face in the moon.”
“But what is that face?”
“It is humanity projected upon the moon. It is a lesson on the powers of
the imagination. We perceive a certain collocation of mountains, peaks,
and plains on the disk of the moon, and our fancy sees in them a human
likeness. We should congratulate ourselves that we are able to do this.
It is a kind of proof of superiority. Many brute animals do not
recognize even their own likenesses in a mirror, much less in a picture.
But the Moon Maiden is perhaps as real as your inhabitants.”
“I am not prepared to confess that yet.”
“Very well, let us go on. The lunar Caucasus is the broader, but
shorter, range of mountains at the northeastern corner of the _Mare
Serenitatis_, and the Alps extend eastward from the Caucasus to a
conspicuous dark oval close to the terminator, which is one of the most
remarkable formations on the moon, and which, when we come to study it
in one of the larger photographs, will probably interest you deeply
because it is one of the places where recent studies have discovered
indications of what may possibly be some form of lunar life. I wish now
to direct your attention to the central and upper parts of the
photograph. Running downward from the south, a little west of the
terminator, you will perceive a double row of immense rings and ring
plains. They are not only remarkable individually, but quite as
remarkable for their juxtaposition in two long ranges. Among them, in
the westernmost row, are three or four whose names you may
remember—Maurolycus, Stöfler, Aliacensis and Werner. Still larger ones
are included in the eastern row, the largest of all being at the bottom.
It is rather a hexagon than a circle. It is 115 miles in diameter, and
the flat plain inside the bordering mountains contains about 9,000
square miles. By close inspection you will perceive a small crater
mountain near the northwestern side. This immense walled plain is named
Ptolemæus after a great astronomer of antiquity, the author of the
Ptolemæic system, which treated the earth as the center of the universe.
“Still more interesting are the things visible farther south. You cannot
fail to remark a very beautiful ring, a perfect circle, brightly
illuminated on the eastern side, and having a bright point symmetrically
placed in the exact center. It is named Tycho, after another great
astronomer, and is generally regarded as the most perfect crater ring on
the moon. It is 54 miles in diameter, and its walls are about 17,000
feet high on the inner side, more than a thousand feet higher than Mt.
Blanc, the giant of the terrestrial Alps. Its central mountain is 5,000
feet high. The most remarkable thing about Tycho is the vast system of
‘rays’ or bands which seem to shoot out from it in all directions,
traversing the surface of the moon, north, south, east, and west for
hundreds of miles, and never turning aside on account of any obstacle.
They lie straight across mountains, valleys, and plains. We have already
seen one of them, the largest of all perhaps, crossing the _Mare
Serenitatis_ and the _Lacus Somniorum_, in the northern hemisphere of
the moon. Nobody knows exactly what these rays mean or what they consist
of. We shall from this time on see them in all the photographs that we
examine, and later I shall have more to say about them, and the
speculations to which they have given rise.
“About half way between Tycho and the south pole of the moon, you will
see an enormous irregular plain, with lofty broken walls, interrupted by
a number of crater rings. Several similar rings also appear in the
interior of the plain. If Tycho is the most perfect in form of the lunar
crater rings, this great inclosure, which is named Clavius, is the
finest example of the walled valleys. It is more than 140 miles across,
and covers an area of not less than 16,000 square miles. Two of the
rings within it, which seem so small in comparison, are 25 miles across.
A smaller walled plain, yet one of really immense size, is seen half way
between Tycho and Clavius, and farther from the terminator than either
of them. This is Maginus, and it possesses the peculiarity that at full
moon it practically disappears!”
“But how can that be possible? I see nothing behind which it can be
hidden.”
“It is the sunlight that hides it. You must have noticed already that
the rings and mountains are best seen when at no great distance from the
terminator, because there the sunlight strikes across them at a low
angle, and their shadows are thrown sharply upon the adjoining slopes
and levels. Look at the western part of the moon in the photograph
before us. Many of the huge rings and walled plains that were so
striking in appearance when the sun was rising upon them are now barely
visible. Langrenus and Petavius, for instance, have become no more than
whitish blotches, and even Theophilus is no longer conspicuous. The
reason is because when the sunlight falls vertically upon any part of
the moon there are no shadows there, and without shadows there can be no
appearance of relief. Then the mightiest mountains are almost lost from
sight in the universal glare. The same thing would be apparent if you
were suspended above the earth at a great height in a balloon and
looking down upon the tops of the snowclad Rockies. Without shadows
serving to reveal their true character and to throw their outlines in
silhouette upon the adjacent plains, they would resemble only white
spots and lines on the generally darker expanse of the continent. But
Maginus is an extreme case. Owing to the relatively small elevation of
its walls, and their broken-up state, and owing also, probably, to a
similarity of color between the mountain ring and the inclosed plain,
when the light is vertical upon them, as at the time of Full Moon, they
blend together and become barely distinguishable from one another, and
from the surrounding surface of the moon.
“Take now photograph No. 9. The age of the moon here is actually less
than it was in the photograph that we last examined, yet, in consequence
of libration, which has caused the moon, in effect, to roll a little to
one side, the sunlight is farther advanced toward the east, and we see
many features of the lunar world that before had not yet emerged from
night. Clavius you will notice is much more fully illuminated. See how
distinctly the shadow of its vast western wall is cast upon the floor of
the valley within, while the opposite eastern wall with its immense
cliffs and precipices glows in full sunshine, its shadow, thrown toward
the east, blending with the darkness of night still covering that side
of the moon. Southeast of Tycho, which is beautifully shown here, two
other great walled plains have come into view. The uppermost of these is
Longomontanus and the other Wilhelm I. For a considerable distance below
these (toward the north) the surface continues broken with rings and
craters, but at length these give place to a dark, level expanse. This
is a part of the _Mare Nubium_, or ‘Sea of Clouds.’”
“Not quite so romantic a name as some of the others,” remarked my
friend, “but still I think I can be sure that Riccioli had nothing to do
with the selection. There is certainly something poetic in the idea of a
sea of clouds.”
“It is a very beautiful region when examined with a telescope,” I
continued, “and its mountainous shores contain many interesting
formations. Farther north, you will observe, near the terminator, and
apparently lying in the midst of the _Mare Nubium_, a large ring, as
perfect in form as Tycho itself. This is a very famous object, and it
bears the name of the great astronomer Copernicus, who overthrew the
Ptolemæic system and established in its place the true idea of the solar
system, namely, that the sun is its center, while the earth and the
other planets revolve as satellites around him.”
“Surely,” said my friend, “Copernicus deserved to have his name placed
in the moon, and very conspicuously, too.”
[Illustration:
NO. 9. AUGUST 2, 1903; MOON’S AGE 8.97 DAYS.
]
“It could not have been made more conspicuous,” I replied, “for the
situation of the great ring mountain called Copernicus, in the midst of
an immense level expanse, makes it one of the most marked features of
the lunar world. Copernicus is the subject of one of the larger
photographs that we are going to examine later, and I reserve a
description of its peculiarities. North of Copernicus you will observe
apparently a continuation of the _Mare Nubium_. But it is really another
‘sea’ that we are looking upon there, the _Mare Imbrium_, ‘Sea of
Rains.’ The baylike projection that runs out into the bright highlands
west of Copernicus bears the name of the _Sinus Medii_, ‘Central Gulf,’
and the one just below it is the _Sinus Æstuum_, ‘Gulf of Heats,’ which
is certainly suggestive of dog days on the moon. Observe that the _Sinus
Æstuum_ merges on the west with a dark, oval area, which is called the
_Mare Vaporum_, ‘Sea of Mists.’ It is one of the darkest districts on
the moon. If you will now turn the photograph upside down you will find
that the _Sinus Medii_ constitutes the dark eye of the Moon Maiden,
while the _Sinus Æstuum_ and the _Mare Vaporum_ form that portion of her
hair which droops upon her forehead.”
“Why not frankly call it frizzed?”
“Because I feared that you would not consider that a sufficiently poetic
term.”
“But I find poetry enough in the names ‘Gulf of Heats’ and ‘Sea of
Mists.’ My admiration for the man who could think of such appellations
continually increases.”
“Then please reverse the photograph, for we must not lose ourselves in
dreams. You will notice that the range of the lunar Apennines runs
between the _Mare Vaporum_ and the _Sinus Æstuum_ on one side, and the
_Mare Imbrium_ on the other. The entire chain of the Apennines is
beautifully shown here. They are exceedingly steep on the side facing
the _Mare Imbrium_, and gigantic peaks standing upon their long wall
cast immense shadows over the ‘sea.’ Their southwestern slopes are
comparatively gentle, rising gradually from the level of the _Mare
Vaporum_. At their upper or southern end, in the direction of
Copernicus, they suddenly terminate with a beautiful ring, which is
called Eratosthenes. This is a fine example of the disk or cup shape of
the lunar volcano. The bottom of Eratosthenes lies 8,000 feet below the
level of the surrounding _Mare_, while peaks on its wall are as much as
15,000 or 16,000 feet in height. Between the lower end of the Apennines
and the upper end of the Caucasus Mountains a strait opens a broad,
level way between the _Mare Imbrium_ and the _Mare Serenitatis_. On one
of the large photographs these two ‘seas’ and the strait connecting them
are represented in all their picturesque details, as you will see when
we come to study them. I promise you at that time a free rein to your
imagination and plenty of room for its flights. On the northern border
of the _Mare Imbrium_ and close to the terminator we see once more the
remarkable oval valley to which I referred when pointing out the lunar
Alps, and which bears the name of Plato. I call your attention to it and
also, again, to Copernicus, in order that you may compare their
appearance here with that which they present in the next photograph,
taken when the moon’s age was eleven and three-quarter days.”
[Illustration:
NO. 10. NOVEMBER 30, 1903; MOON’S AGE 11.78 DAYS.
]
We hereupon turned to photograph No. 10.
“Now,” I continued, “observe the difference that some two days’ advance
of the sunlight has produced. Plato is far within the illuminated part
of the disk, and it looks darker than before. Copernicus, on the other
hand, which appeared as a sharp ring with one border dark when it was
near the sunrise line, has now become a round, white spot, somewhat
darker in the center, with a great grayish splatter surrounding it upon
the surface of the _Mare_. In the meantime, over nearly the whole extent
of the _Mare Imbrium_ the sun has risen and two other _mares_ have made
their appearance, one of which, extending across half the width of the
eastern hemisphere, might be called the Pacific Ocean of the moon, if it
had any water. It is named the _Oceanus Procellarum_, the ‘Ocean of
Tempests,’ while at its southern extremity a very dark nearly circular
expanse, inclosed with mountains, bears the name of the _Mare Humorum_,
‘Sea of Humors.’”
“Evidently the astronomer who bestowed that name was not in a joking
mood else he would surely have called it the ‘Sea of Humor.’”
“No, apparently he was in deep earnest. But what kind of humors he was
thinking of I cannot tell. Perhaps the name occurred to him because the
_Mare Humorum_ is the darkest of all the great levels on the moon. It is
very conspicuous to the naked eye at Full Moon. You will perceive that
Tycho has now become the most prominent of all the rings on the moon. It
will maintain this distinction and continue to gain in conspicuousness
up to the time of Full Moon. Seen as we now see it, Tycho manifestly
merits the appellation sometimes bestowed upon it of the ‘metropolitan
crater of the moon.’ Notice how bright the mysterious bands radiating
from it have become. The higher the sun rises upon them the more
brilliantly they glow, almost as if they were streaks of new-fallen
snow. They spread over the whole of the southwestern quarter of the
moon, hiding rings and mountains with their brightness. One very notable
ray runs down into the _Mare Nubium_, and a fainter one parallel with it
produces the semblance of a long, walled way.
“The South Pole of the moon lies in the midst of a marvelously upheaved
and tumbled region, where one huge ring is seen breaking into another on
every hand. One of these rings, named Newton—it lies just on the upper
edge of the disk, south of Clavius—surrounds the deepest known
depression on the moon. Its bottom sinks to a depth of 24,000 feet below
the highest point on the wall. This gigantic hole is so profound that,
situated where it is, close to the pole, where the sun can never rise
very high, its depths remain forever buried in night. It is the very
ideal of a dungeon, for if you were imprisoned at the bottom you would
never see either the sun or the earth.”
“You make me shudder! Truly, after all, the moon appears to be a world
filled with dreadful things. Who would ever imagine it, seeing how
serene and beautiful she is in a calm night?”
“Yet is there not a kind of beauty even in those things, like the abyss
of Newton, which appall you only when you know the real facts about
them? There is a certain grace in their shapes and outlines, and a great
attraction for the eye in their contrasts of light and shadow. It is the
same sort of attraction which we find in such terrestrial scenes as the
Yosemite Valley viewed from Inspiration Point, or the awful depths and
chasms of the Grand Cañon of the Colorado. The presence of man and his
works is not always essential in order to fix our attention upon the
wonders of nature. Their very grandeur exalts us until we forget our
little race and its ephemeral achievements.”
“Still, I hope that you will show me something on the moon less
awe-inspiring and suited to awaken more quiet thoughts, and especially
to reassure me concerning my lunarians, as I suppose you would call
them.”
“You shall not be kept long in expectation. Turn your eyes once more to
the _Mare Imbrium_. You will observe that its northern shore consists of
a series of curves, each terminating with a promontory projecting into
the sea. When looking at it I am often reminded of an entrancing view
which I once enjoyed from the summit of Mt. Etna over the island of
Sicily. From that great elevation nearly the whole eastern and
southeastern coast of the island was visible as upon a map. The indented
shore stretched away in long, graceful curves, where the blue
Mediterranean contrasted sharply with the yellow sands, and the eye,
wandering from Catania to Syracuse, was enchanted with the beauty of
those geometric lines. But the winding coast of the _Mare Imbrium_ is
far longer than the shores of Sicily, and the mountains and cliffs
bordering it are more wonderful than any corresponding scenes on the
earth. I wish, particularly, to have you look at the easternmost of the
indentations on the northern side of the _mare_. It bears a designation
that must surely please your imagination. It is the _Sinus Iridum_,
‘Gulf or Bay of Rainbows.’”
“I recognize the work of my old friend the unknown astronomer. Verily he
had a poetic soul! And he has written his poem on the chart of the moon,
for those to read who can.”
“It is a charming landscape that the telescope reveals there,” I said,
“even though no rainbows are visible.”
“But you will not deny that they may once have spanned that bay and its
shores with their exquisite arches?”
“No, I shall not deny so pleasing a possibility. I will only say that it
lies beyond the ken, and even outside the field, of science.”
“Then I regard it as fortunate that _he_ was not too exclusive in his
devotion to science, for then he could never have seen the rainbows with
the eye of fancy, and your charts would not have been adorned with so
delightful a name.”
“Let me tell you about this bay or gulf,” I said, tapping the photograph
to recall her from her reverie. “You observe that it terminates at each
end with a promontory. That at the western end is named Laplace, and the
other Heraclides. The latter is the more picturesque. If ever you have
an opportunity to see the moon with a good telescope do not fail to look
at the promontory of Heraclides, for if you are fortunate in the choice
of the time of observation when the setting sun is throwing its shadow
over the adjoining ‘bay,’ you will find that the serrated outlines of
the promontory represent, in a very striking manner, the profile of a
woman, more sharply defined than the face of our familiar Moon Maiden,
but a mere miniature in relative size. The shores of the _Sinus Iridum_
are bordered with high cliffs, behind which rise the peaks of a mighty
mountain mass. Just back of the center of the great bowed shore of the
‘bay’ appears, in the photograph, a small, bright crater ring. This
bears the name of Bianchini. It is a lunar volcano, 18 miles in
diameter, rising out of the midst of many ranges of nearly parallel
hills and mountains, the general direction of which corresponds with
that of the shore of the ‘bay.’ If there is any place on the moon where
one is tempted to think that the scenes of a living world might once
have been witnessed it is the _Sinus Iridum_ and its neighborhood. Its
latitude is between 40° and 50° north, corresponding with the most
thickly populated zone of our own globe. The surface of the ‘bay’—once
its bottom, if we admit that it was ever filled with water—is gently
undulating, with winding ridges that suggest the action of tides and
currents in sweeping to and fro deposits of sand and gravel, and piling
them in long rows of bars and shallows. One can hardly help picturing in
the mind’s eye waves breaking on the curving beach and dashing against
the projecting rocks of the promontories; a white city seated just at
the center of the shore of the ‘bay,’ near Bianchini, like Naples at the
feet of Vesuvius; a rich vegetation covering the slopes of the mountain
valleys, and romantic sails dotting the ‘bay’ and the neighboring
‘sea.’”
“I am very glad to observe,” interrupted my friend, “that you are not
hopelessly prejudiced against my opinion that the moon has not always
been ‘dead,’ as you call it.”
“I am so far from it,” I replied, “that I am half disposed to admit that
she is not altogether dead even yet. But it is my duty to keep you as
close as possible to the known facts. We shall see the _Mare Imbrium_
and the neighborhood of the ‘Bay of Rainbows’ again. Meanwhile, suppose
we turn to the next photograph of the series, No. 11. The age of the
moon here is about thirteen days. She is fast approaching the phase of
Full Moon. The first thing to which I would direct your attention now is
the exceedingly brilliant point of light which has come into view near
the terminator, a little north of east where the _Mare Imbrium_ merges
into the _Oceanus Procellarum_. In several ways this is the most
noteworthy object on the moon. It led the famous English astronomer, Sir
William Herschel, to believe that he had seen an active volcano on our
satellite. He naïvely wrote in his notebook on a certain occasion: ‘The
volcano glows more brightly to-night!’ Yet it is no more active than the
other craters and crater rings in the lunar world. It is only
extraordinarily, almost incredibly brilliant—by far the most dazzling
point on the moon. It is a ring mountain, and is named Aristarchus. It
has a near neighbor, barely visible in this photograph, close by toward
the east named Herodotus. Herodotus is by no means remarkable for
brilliancy. The central peak and a part of the floor and the east wall
of Aristarchus consist of some material—nobody can tell what it is—which
gleams in the sunlight, I had almost said like diamonds, although that
would be an exaggeration. There are three or four other crater rings on
the moon, including Proclus, which are also very brilliant, but not one
of them can be regarded as a rival of Aristarchus. Its power of
reflection is so great that it is even visible with a telescope in the
lunar night, when the only light of any consequence that reaches it is
that sent from the earth. It was, indeed, this fact which misled
Herschel. He saw Aristarchus shining on the night side of the moon, and
naturally thought that only the fires of an active volcano could have
rendered it thus visible.”
[Illustration:
NO. 11. DECEMBER 1, 1903; MOON’S AGE 12.98 DAYS.
]
“And are you sure that he was mistaken?”
“Positively. There is no fire in Aristarchus, and has been none for
ages.”
“But why do not astronomers undertake to find out what it is that makes
Aristarchus so brilliant, then?”