Just on the southern border of the _Mare_, the beautiful ring Menelaus lies in the center of the chain of the Haemus Mountains. The ring is about twenty miles across, and its central peak is composed of some highly reflecting material, so that it shines very bright. The streak or ray from Tycho which crosses the _Mare Serenitatis_ passes through the walls of Menelaus, and perhaps the central peak is composed of the same substance that forms the ray. Something more than a hundred miles east-southeast from Menelaus, in the midst of the dark _Mare Vaporum_, is another brilliant ring mountain which catches the eye, Manilius. It exceeds Menelaus in brightness as well as in size, its diameter being about twenty-five miles. There is something singular underlying the dark lunar surface here, for not only is Manilius extraordinarily brilliant in contrast with the surrounding plain, but out of that plain, about forty miles toward the east, projects a small mountain which is also remarkable for its reflecting properties, as if the gray ground were underlain by a stratum of some material that flashes back the sunlight wherever it is exposed. The crater mountain, Sulpicius Gallus, on the border of the _Mare_, north of Manilius and east of Menelaus, is another example of the strange shining quality of certain formations on the moon. Follow next the Haemus range westward until the attention falls upon the great ring mountain Plinius, more than thirty miles across, and bearing an unusual resemblance to a fortification. Mr. T. G. Elger, the celebrated English selenographer, says of Plinius that, at sunrise, "it reminds one of a great fortress or redoubt erected to command the passage between the _Mare Tranquilitatis_ and the _Mare Serenitatis_." But, of course, the resemblance is purely fanciful. Men, even though they dwelt in the moon, would not build a rampart 6,000 feet high! Mount Argaeus, at the southwest corner of the _Mare Serenitatis_, is a very wonderful object when the sun has just risen upon it. This occurs five days after the new moon. Returning to the eastern extremity of the _Mare_, we glance, in passing, at the precipitous Mount Hadley, which rises more than 15,000 feet above the level of the _Mare_ and forms the northern point of the Apennine range. Passing into the region of the _Mare Imbrium_, whose western end is divided into the _Palus Putredinis_ on the south and the _Palus Nebularum_ on the north, we notice three conspicuous ring mountains, Cassini near the Alps, and Aristillus and Autolycus, a beautiful pair, nearly opposite the strait connecting the two _Maria_. Cassini is thirty-six miles in diameter, Aristillus thirty-four, and Autolycus twenty-three. The first named is shallow, only 4,000 feet in depth from the highest point of its wall, while Aristillus carries some peaks on its girdle 11,000 feet high. Autolycus, like Cassini, is of no very great depth.