HERSCHEL.—­A typical ring-plain, situated just outside the N. border of Ptolemaeus, with a lofty wall rising nearly 10,000 feet above a somewhat dusky floor, which includes a prominent central mountain.  Its bright border is clearly terraced both within and without, the terraces on the inner slope of the W. wall being beautifully distinct even under a high light, and on the outer slope are some curious irregular depressions.  On the S.S.E. is a large oblong deep crater, close to the rocky margin of Ptolemaeus, and a little beyond the foot of the wall on the N.W. is a smaller and more regular rimmed depression, b, standing near the E. border of the great valley, more than 80 miles long, and in places fully 10 miles wide, which runs from S.S.W. to N.N.E. on the W. side of Herschel, and bears a close resemblance to the well-known Ukert Valley.  Herschel d is a large but shallow ring-plain on the E. of Herschel, with a brilliant but smaller crater on the W. of it.

North of Herschel, on a plateau concentric with its outline, stands the large polygonal ring-plain Herschel a, a formation of a very interesting character, with a low broken wall, exhibiting many gaps, and including some craters of a minute class.  The largest of these stands on the S.W. wall.  Mr. W.H.  Maw has detected some of these objects on the N. side, both in connection with the border and beyond it.

FLAMMARION.—­A large incomplete walled-plain N.E. of Herschel, open towards the N., with a border rising about 3000 feet above the floor.  The brilliant crater, Mosting A, stands just outside the wall on the E.

PTOLEMAEUS.—­Taking its very favourable position into account, this is undoubtedly the most perfect example of a walled-plain on the moon’s visible superficies.  It is the largest and most northerly component of the fine linear chain of great enclosures, which extend southwards, in a nearly unbroken line, to Walter.  It exhibits a very marked departure from circularity, the outline of the border approximating in form to a hexagon with nearly straight sides.  It includes an area of about 9000 square miles, the greatest distance from side to side being about 115 miles.  It is, in fact, about equal in size to the counties of York, Lancashire, and Westmorland combined; and were it possible for one to stand near the centre of its vast floor, he might easily suppose that he was stationed on a boundless plain; for, except towards the west, not a peak, or other indication of the existence of the massive rampart would be discernible; and even in this direction he would only see the upper portion of a great mountain on the wall.