Part 11

“South of Kies, at the edge of the _Mare Nubium_, is a lofty mountain range whose summits and slopes are very bright in the sunrise. At one point a great pass breaks through these mountains, leading to a sort of bay shut in on all sides by precipices and the walls of gigantic crater rings. The large crater ring at the eastern corner of this bay is Capuanus. The smaller ring on its western side with a conspicuous crater on its eastern wall is Cichus. Notice the fine shadow that Cichus casts, whose pointed edge is evidently due to the little crater on the wall. That ‘little’ crater is six miles across! The twin rings apparently terminating the mountain mass northeast of the bay are Mercator and Capuanus. Between these and Kies you perceive two short ranges of small mountains and then a kind of round swelling of the surface of the plain resembling a great mound. These formations are rare on the moon. They look like bubbles raised by imprisoned gases. The United States Geological Survey has discovered something similar in form, but infinitely inferior in magnitude, in the great mud bubbles that rise to the surface of the Gulf of Mexico off the mouth of the Mississippi River. But I do not mean to aver that the two phenomena are similar in origin.

“Near the southern shore of the _Mare Nubium_ appears a long, dark line which starts at the edge of a crater ring, crosses the southern arm of the ‘sea,’ evidently penetrates the bordering mountains, and reappears traversing the dark bay near its northern edge, cleaving both walls of a small crater ring in its way.

“I should weary you, perhaps, with too much detail if I undertook to identify all of the prominent objects in this photograph. Returning to the southern shore of the _Mare Nubium_, I shall simply call your attention to the very large ring plain with terraced walls and a peak a little east of its center. This is Pitatus. An enormous ravine breaks through its eastern side and connects it with a smaller ring from which the dark line already mentioned starts. This dark line represents one of the most remarkable clefts on the moon. It looks as though the crust had been split asunder there over a distance of at least 150 miles. It bears some resemblance to the great cañon near Aristarchus and Herodotus, except that the latter is very tortuous and this is nearly straight.”

“Have I not heard of something similar in connection with the California earthquake in 1906?” asked my friend.

“No doubt you are thinking of the great ‘fault’ which geologists have discovered off the Pacific coast of North America. There is perhaps some resemblance between these phenomena. Pitatus, I may add, is 58 miles in diameter. You will observe how its southern wall has apparently been broken down by the deluge of lava which buried so many smaller rings in the _Mare Nubium_. If you will now turn your attention to the left-hand side of the photograph, somewhat above the center, you will perceive a very strange object, the so-called ‘Straight Wall.’ It lies just west of a large conical crater pit which has a much smaller pit near its western edge. You might easily mistake the ‘Straight Wall’ for an accidental mark in the photograph. It is not absolutely straight, and near its southern end it makes a slight turn eastward and terminates in a curious, branched mountain, whose most conspicuous part is crescent-shaped. The wall is about 65 miles in length and 500 feet in height. It is as perpendicular on its east face as the Palisades on the Hudson. It is not a ridge of hills at all, but a place where the level of the ground suddenly falls away. Approaching it from the west you would probably be unaware of its existence until you stood upon its verge. The dark line that we see in the photograph is the shadow cast by the wall upon the lower plain. In the lunar afternoon the appearance is changed, and the face of the cliff is seen bright with sunlight. This curious object has attracted the attention of students of the moon for generations, and many speculations were formerly indulged in concerning its possible artificial origin. It has sometimes been called the ‘Lunar Railroad.’ Manifestly, whatever else it may be, it is not artificial. The closest analogy perhaps is with what we were speaking of a little while ago, a geological fault, that is to say, a line in the crust of the planet where the rocky strata have been broken across and one side has dropped to a lower level.

“The crater pit in the _Mare Nubium_, east of the ‘Straight Wall,’ is named Birt, and its twin, 75 miles farther east, is Nicollet. Look now at the hooked nose of your ‘dark woman.’ The huge wart upon it is a crater plain named Lassell. Between the lower end of the ‘Straight Wall’ and Lassell, and over the bridge of the ‘nose,’ a wedge-shaped mountain runs out into the _mare_. This is called the Promontorium Ænarium, and must have formed a magnificent outlook if ever a real ocean flowed at the foot of its cliffs. The ring with a crater on its wall below Lassell is Davy. You will note some very somber regions scattered over this part of the _Mare Nubium_. One of them forms the ‘dark woman’s’ eye, and just over it, like an eyebrow, is a curving range of hillocks, including some little craters. On the ‘cheek’—I am still utilizing the ‘dark woman’ as a kind of signboard—at the base of the ‘chin,’ appears a partly double range of large ring plains. The greatest of these, at the bottom, is named Fra Mauro, and you will notice within it a curious speckling of small craters. Adjoining Fra Mauro on the south are two intersecting rings, Barry being the name of the western and Bonpland that of the eastern one. The partially submerged ring is nameless, as far as I know, while the upper or southern member of the group, with a broad valley shut in between broken mountain walls opening out of its northern side, is Guerike. There is only one other object, on the extreme lower right-hand corner of the picture, to which I will ask your attention. It is a singular range of mountains thrown into a great loop at its northern end, and known as the Riphæan Mountains.”

“It seems to me,” said my friend, putting her elbow on the table, and leaning her head a little wearily on her hand, “that there is a great sameness in these lunar scenes—always crater rings with or without central mountains, always peaks and ridges and chasms and black shadows. Truly variety is lacking.”

“But what could you expect?” I replied. “Is it not enough to stimulate your curiosity that you are looking intimately into the details of a foreign world? When you go to Europe you see there mountains, plains, rivers, lakes, cities, people, absolutely identical in their main features with what you see in America. But you find them endlessly interesting because of their comparatively slight differences from similar things with which you are familiar, because of the great age of many of the objects to which your attention is directed, because of the long course of history which they represent, and principally, perhaps, because you are aware of the sensation of being far from home. It ought to be the same for you here on the moon. These things that we are looking upon belong to a globe suspended in space 239,000 miles from the earth. If the features of our globe are practically the same everywhere, differing only in the arrangement of their details, you should not be surprised at finding that nature does not vary from her rule of uniformity on the moon.

“In the next photograph of the series,” I continued, “we have a marvelous specimen of the lunar landscapes. It is perhaps the most rugged region on the moon. It includes two objects of supreme interest, Tycho, the ‘Metropolitan Crater,’ and Clavius, the most remarkable of the ring plains. You will no doubt recognize Tycho at a glance. It is near the center of the picture. Like the last photograph this one represents an early morning scene. The western wall of Tycho throws a broad, irregular crescent of shadow into the cavernous interior, but all of the eastern, northern, and southern sides of the wall are illuminated on their inner faces. The central mountain group is emphasized by its black shadow. A little close inspection reveals the existence of the complicated system of terraces by which the walls drop from greater to lesser heights until the deep sunken floor is reached. The diameter of Tycho is 54 miles, and it is at least 17,000 feet deep, measured from the summits of the peaks that tower on both the eastern and the western sides of its wall. The vast system of bright streaks radiating from Tycho is not seen here, the time when the photograph was made being too near the sunrise on this part of the moon. The dish-shaped plains crowded around Tycho form a remarkable feature of this part of the lunar surface. It would be useless to mention them all by name, and I shall ask your attention only to some of the principal ones.”

“Thank you for being so considerate,” said my friend, smiling. “I am sure that I should forget the names as fast as you mentioned them.”

“Oh, I have no fault to find with your memory,” I replied. “I doubt if 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.”

“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.”