“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.”