The Moon: A Popular Treatise

by Garrett Putman Serviss

“That is the promontory which presents the profile of a woman’s face, if I recall correctly what you told me.”

“Yes. Please observe also that the oval of Plato is as dark as ever, while Copernicus has, if possible, increased in brightness, and the great splatter of broken rays around it seems to have extended farther over the surrounding maria. Almost directly east of Copernicus, in the Oceanus Procellarum, appears a much smaller crater ring, Kepler, which resembles a miniature of Copernicus because it, too, is encircled with a kind of corona of short, bright rays. Copernicus, Kepler, and Aristarchus mark the corners of a large triangle. Speaking of rays recalls us to Tycho. You will see that, as I told you, this wonderful formation grows in relative prominence when the period of Full Moon approaches. Its ringed wall and central mountain are obscured by their own brilliance, while the gigantic system of bright bands, or rays, which have their center of origin at Tycho, is gradually becoming the master feature of the bright part of the moon.

“I have told you that the Mare Humorum, which is very sharply defined in the picture before us, is the darkest of all the level areas that go under the name of ‘seas.’ It is not, however, the darkest spot on the moon. There are several places where the surface appears, at times, much duskier than in any part of the Mare Humorum. Three or four of these are clearly discernible in this photograph. They lie westward from Copernicus in the Sinus Medii, the Sinus Æstuum, and the Mare Vaporum. Their dusky hue strikes the eye at once. They give the impression of sink holes. No special name is attached to them, but they must have been evident to the first observers, with the smallest telescopes, and it is rather surprising they should have escaped special designation on the lunar charts. A fact which will especially interest you is that some observers look upon these and other dusky areas on the moon as being, possibly, indications of the existence of some kind of vegetation there.”

“But if there is vegetation there may be other kinds of life also, may there not?”

“Ah, I have not said positively that there is vegetation, but if there is then your conclusion as to other life may be correct. Glance next at the upper part of the disk along the terminator. Two or three broad oval rings have come into view there. The largest of these with its long eastern wall lying exactly on the line between day and night is an extremely interesting formation, bearing the name of Schickard. The plain within the ring is almost large enough to have been called a ‘sea’ or at least a ‘lake.’ It is about 134 miles in diameter, and is in reality much more nearly circular than it appears to be. Like all similar formations situated near the ‘limb’ of the moon, by which we mean the edge as viewed from the earth, it is greatly foreshortened by perspective. The scale of the photograph is, unfortunately, not large enough to reveal an unique thing in the immediate neighborhood of Schickard, toward the southeast. I refer to what, as far as its telescopic appearance goes, might be described as an enormous bubble—a bubble 54 miles in diameter. Unlike the other formations the surface of this singular ring is elevated above the general level of the moon. When we come to examine it in detail it hardly answers, perhaps, to my designation of a bubble, since the edges are a little higher than the center, giving it the form of a shallow dish. If we could visit it we should find on approaching that we were climbing the slopes of what would seem to be a chain of low mountains, and on reaching the summit we should see before us an elevated circular plain, sinking gradually toward the middle. Filled with water it would form a shallow lake lying on the top of a broad, flat mountain. There is nothing else quite like it on the moon and certainly nothing on the earth.”

“It must have been a great curiosity in the days when the moon was inhabited, and I suppose that scientific ‘lunarians’ organized expeditions to explore it.”

“Perhaps, if you choose to regard it in that way. Now look again at the Mare Humorum. You perceive that its eastern side is lined with mountains and crater rings, while near the center of the northern border there is a conspicuous ring with a bright line running from the southern edge to the center. This is one of the most beautiful of lunar formations, and is named Gassendi. It is a favorite object for those who study the moon with telescopes on account of the great variety and singularity of the details visible within the ring. When you become a selenographer and possess your own telescope you will find few things more interesting to study than Gassendi.

“Next let us take up photograph No. 12. Here the moon is once more a little ‘older’ than before, and the sunrise line has again advanced a little eastward. This advance does not appear so rapid when the terminator is near the moon’s limb, because, on account of the rounding away of the lunar globe, the illuminated surface is foreshortened from our point of view on the earth. In this photograph you perceive that the wonderful shining mountain Aristarchus has become even brighter than it was before, or at least it is more conspicuous on account of the appearance of what seems to be a short ray shooting out from it in a southeasterly direction. There is also a light spot just below it which is caused by a little mountain group called the Harbinger Mountains. The bright ray connects Aristarchus with its neighbor Herodotus, of which I spoke a little while ago. There is a very remarkable feature of the moon here, not shown in the photograph, but to which I must briefly refer. It is an enormous cleft, or crack, or, if you please, cañon, which starts from Herodotus, whose northern wall seems to have been broken through to give passage to it, and goes winding across the surface of the Oceanus Procellarum with several sharp turns and angles for a total distance of nearly a hundred miles. What produced this remarkable chasm on the moon it is difficult to say. Some have suggested that it may once have been the bed of a river, but there are many serious objections to that view. Nevertheless, there seems to be little doubt that if we were to visit the moon we should find, in many ways, a striking resemblance between this prodigious cañon and that of the Colorado River.”

“And are not all these things so ancient, as far as you can tell, that, like the terrible volcanic rings, they might have been formed before the appearance of inhabitants upon the moon?”