Part 10

“Below Stöfler, all along the terminator, as far as the middle of the moon, an irregular row of rings appears. Three of these bear some resemblance to the great group of which Theophilus is the chief member. They are, counting from south toward north, Aliacensis, Werner, and Blanchinus. Below them two other much larger ones are conspicuous, Albategnius, the more southerly, and Hipparchus. These two are full of moon history. Albategnius, the smaller, is very deep and comparatively perfect in condition, while Hipparchus, more than 90 miles across, has been vividly described as a ‘wreck and ruin,’ its walls, once possibly of great height, being now low and broken, and traversed with gaps and valleys, while a great cleft exists crossing a part of the broad, irregular floor. It is probable that Hipparchus is an older formation than Albategnius.”

NO. 6. NOVEMBER 26, 1903; MOON’S AGE 7.75 DAYS. ]

“Pardon me,” interrupted my companion, “but I must cry for mercy. Really, these strange names escape from my mind as fast as you mention them. Is there not something a little more romantic in the moon—something to relieve the strain of all this nomenclature of words terminating in ‘us,’ and this frightful lunar geology?”

“Yes,” I said, “I believe that on the other half of the moon, which has not yet seen the sun rise, we shall find something better to your taste. But do not be too impatient. Reflect that these names represent very wonderful things visible to us in another world than ours, things the knowledge of which has cost the lifelong labors of many gifted men, and that will be remembered, studied, talked, and written about centuries after we are dead. Fortunately for your powers of attention the eastern half of the moon, upon which day will be seen gradually dawning in the next set of photographs, has a general character quite different from that of the western half. It contains the greatest ranges of lunar mountains, yet upon the whole it is more level, being covered to a great extent with broad plains, in the midst and along the borders of which stand the most remarkable and interesting of all the lunar formations. In and around some of them we shall search for the evidences which some astronomers think that they have found of life upon the moon.”

“Oh, that indeed will be interesting!” exclaimed my friend with reviving animation.

“But,” I added, “do not place your expectations too high. Keep your imagination under control, try always to be just a little ‘scientific’ in your way of looking at things, and then I believe you will not be disappointed.”

“Oh, please do not think that I have been disappointed,” she said deprecatingly. “But positively you must admit that ‘Albategnius,’ ‘Aliacensis,’ ‘Blanchinus,’ and ‘Maurolycus,’ are not precisely captivating. Remember that I have read little except poetry and romance, and those histories that are full of stories.”

“You will find a deep vein of poetry and romance in the moon,” I replied, “before we have finished, and after you have reflected upon what we have seen and what we have been saying.”

Leaving the remaining photographs to be examined after lunch, we now entered the house.

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FIRST QUARTER TO FULL MOON

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FIRST QUARTER TO FULL MOON

NOTWITHSTANDING the signs of impatience which my friend had manifested when we were passing, in our review of the photographs, from one lunar ring mountain to another, all more or less similar in appearance and characteristics, I was gratified to see that her mind was still attracted to the subject of the moon, and during the lunch she, of her own accord, began to talk of it.

“You have said so much about volcanic occurrences on the moon,” she remarked, “that I wonder why you do not call those immense mountains ‘volcanoes.’ I observe that you always speak of them as ‘rings,’ or ‘mountain rings,’ or ‘ring plains’; while to me, although to be sure I am no geologist and have perhaps no right to an opinion, they seem plainly to be just huge volcanoes and nothing else.”

“Your observation is quite correct,” I replied, “as far as superficial appearance goes, and I may add that these great rings are often called volcanoes. If we apply the proper adjective and name them ‘lunar volcanoes,’ perhaps there can be no objection to the term. But they are certainly widely different from our terrestrial volcanoes. The difference is not in size alone, although in that regard it is enormous. There is a far more significant difference, which you could hardly be expected to notice in a simple inspection of the photographs, although it is evident when once pointed out. I refer to the fact that what seem to be the craters of lunar volcanoes are not situated on the tops of mountains. They are immense plains, more or less irregular in surface, and often having a peak or a group of peaks in the center, while around these plains always extends a mountain ring, steep on the inner side, and having a gradual slope without. But most significant fact of all, the plains, or floors inside the ring, are almost invariably situated thousands of feet below the general level of the moon. If the terrestrial volcanoes were formed on the plan of the lunar ones, when we visit Vesuvius, instead of climbing up a mountain rising out of the midst of a plain and capped with a cone, having a funnel-shaped crater in the center, we should find before us a relatively low, circular elevation, on surmounting which there would appear on the inside of the circle a great basinlike hollow, far below the level of the surrounding country. In the center of this, distant from the lofty encircling walls, would be seen a conical hill with smoke and vapor issuing from a vent at its summit. The top of this crater hill would be lower than the rim of the basin-shaped hollow, so that the whole volcano with its immediate surroundings would be inclosed and shut off from the environing upper world by the sides of the basin. While you finish your coffee I will make a sketch which may render this difference between lunar and terrestrial volcanoes evident at a glance.”

Lunar Volcano, in Section. ]

Terrestrial Volcano, in Section. ]

Accordingly, after a few minutes, I presented to her these two diagrams, remarking that it should be borne in mind that the two sketches were not made on the same relative scale. “I was compelled,” I said, “to change the true proportions in the section of the lunar volcano, for if I had drawn them as they are in fact, the width of the basin would have been enormous in proportion to its depth. You will recall that I told you that such rings as Albategnius and Maurolycus are a hundred miles and even more in diameter, while their depth does not exceed two or three miles. It results from this necessary falsification of proportions in the sketch that the terrestrial volcano, although so widely different in form, appears comparable in magnitude with the lunar one. But the fact is that you could take a dozen of the largest volcanic mountains on the earth and throw them into one of the great lunar rings without filling it.”

“I am the more astonished by what you say,” remarked my friend, “because you have already told me that the moon is so much smaller than the earth. How does it happen, then, that her volcanoes are so much larger? I should think that in a little world all things would be small in proportion.”

“It is quite natural to think so,” I replied, “until you reflect upon the consequences of the smaller force of gravitation on a small world. I told you last evening that gravitation on the moon, is only one sixth as powerful as it is on the earth, and you will recall that one consequence which I pointed out was that you would weigh only twenty pounds if you were on the moon. Since the same reasoning applies to all objects in the lunar world, it is clear that a similar force exerted there would be able to produce enormously greater effects, as for instance in the formation of vast hollows or depressions, by violent explosions, the products of which would be thrown to immense distances. Some selenographers, which is a term applied to those who study the features of the lunar world, have suggested that in this cause alone is to be found the explanation of the giant lunar ring mountains. At some remote period of the past, according to them, the volcanic forces of the moon reached a maximum of activity and energy. The lava, cinders, ashes, and other products of ejection, were hurled to a height of scores of miles, and when this fell back at a great distance from the centers of eruption these were piled up in huge rings, fifty, eighty, or a hundred miles in diameter, while the surface of the moon within the rings sank in consequence of the withdrawal of the material thus ejected. To account for the existence of the central mountains so often found in the middle of the rings, it has been suggested that at a much later period, when the volcanic energy had become comparatively insignificant, as a result of the cooling of the interior of the moon, less violent explosions, not greater than many that have occurred on the earth, took place, and by these the central peaks were formed.”

“You are going to think me too romantic, or too imaginative, again,” said my friend, with a smile, “but I cannot prevent myself from wondering what the inhabitants of the moon did and thought while all those marvelous things were happening.”

“I have not said that there were inhabitants of the moon.”

“No, but you have confessed that there might have been inhabitants, some time, and I should like to know whether they were there when those terrible volcanoes were formed.”

“If they were,” I replied, “they could not have survived such a universal upheaval as the surface of the moon has undergone. You have seen in the photographs that the great rings and smaller craters are scattered thickly over the moon. It is true that comparatively few are found in the level expanses called ‘seas,’ but if those regions were covered with water they could only have been inhabited by beings provided with gills and fins.”

“How long ago did these explosions occur?”

“I cannot tell you, except that it must have been many ages in the past; so long ago, indeed, that the whole course of human history seems but a day in comparison.”

“Then,” said my friend with animation, “there has been time enough since that dreadful period for inhabitants to develop upon the moon, has there not?”