_Copernicus._ A magnificent ring-plain, 56 miles in diameter, and surrounded by a wall (in which there are terraces and lofty peaks, separated by ravines) attaining an elevation of 11,000 feet. There is a central hill of nearly 2500 feet. From Copernicus light-streaks are plentifully extended on all sides, and apparently connect this object with the many others of similar character which are situated in this region. Neison says that near Copernicus the light-streaks unite and form a kind of nimbus or light-cloud about it. The streaks are most conspicuous towards the N., where they are from 5 to 14 miles in width. To the N.W. of Copernicus, about halfway in the direction of the neighbouring ring-plain _Eratosthenes_ (and N. of Stadius), there is a considerable number of crater-pits. Mädler figured sixty-one of these, and regarded that number as certainly less than half the total number visible. They appear to be ranged in rows or streams, and are so close together in places as to nearly form crater-rills. Schmidt saw the ground hereabout pierced like a honeycomb, and managed to count about 300 little craters; but they are so thickly strewn in this district that exact numbers or places cannot be assigned. They are best observable when the Sun is rising on the E. wall of Copernicus. The interior of this fine object shows six or seven peaks, which are often capped with sunshine, and very brilliant amid the black shadow thrown from the surrounding wall. _Theophilus._ Another ring-plain, and one of the deepest visible. Its terraced lofty wall, 64 miles in diameter, rises in a series of peaks to heights varying between 14,000 and 18,000 feet. There is a central mountain, broken by ravines; but from one of the masses a peak ascends to a height of about 6000 feet. _Petavius._ A large walled plain, surrounded by a double wall or rampart, which rises to 11,000 feet on its E. side. There are hills and ridges in the interior, and a central peak, A, reaching to 5500 feet above the E. part of the floor, which is convex in form. A smaller peak, of nearly 4000 feet, lies W. of A. Several small craterlets have been seen in the interior. _Newton._ The deepest walled plain known upon the Moon’s surface. In form it is elliptical; its length is 143 miles, while its breadth is only 69 miles. The walls show the terracing so common in these objects, and one lofty peak reaches the unusual height of 24,000 feet above the floor. The interior includes some small craters, mountain protuberances, and other irregularities. Neison says that, owing to “the immense height of the wall, a great part of the floor is entirely lost in shadow, neither Earth nor Sun being ever visible from it.” [Illustration: Fig. 26. Petavius and Wrottesley at sunset. 1885, Dec. 23, 9^h to 10^h 30^m. (T. Gwyn Elger.)]