“I was about to speak of that. It is a ring plain named Lubiniesky, about 23 miles in diameter with a wall a thousand feet in height, except in the direction of Bullialdus where it is broken down. The interior is very flat, and it forms a fine example of the half-submerged lunar volcanoes which abound in this hemisphere. It may have had a central mountain like Bullialdus, but if so it has been completely buried under the influx of molten lava or whatever it was that covered this part of the moon. The perfect form of Bullialdus in all its details when compared with the mere outline that remains of Lubiniesky indicates that the former probably burst forth after the inundation of liquid rock that drowned the latter. Thus we have in these two neighboring formations two chapters of lunar history which, like the monuments of Egypt, tell the story of widely separated epochs. The row of still more completely submerged crater rings westward from Lubiniesky and Bullialdus show by their condition that the depth of the lava flood was probably greater in their vicinity than it was farther eastward. “Now look southward from Bullialdus, at a distance about twice as great as that of Lubiniesky and you will see another partially submerged ring, with a more serrated crest. The name of this is Kies. It is remarkable for the lofty mountain spur which sets off from its southern wall, and also for the fact that one of the bright streaks from Tycho—one of a parallel pair that I pointed out to you last evening—traverses its flat floor and continues on, broadening as it goes, to a deep crater ring which we have already noticed, southeast of Bullialdus. “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.