BESSARION.—­A bright little ring-plain, about 6 miles in diameter, in the Oceanus Procellarum N. of Kepler.  There is a smaller and still brighter companion on the N. (Bessarion E), standing on a light area.  Bessarion has a minute central hill, difficult to detect.

PYTHEAS.—­A small rhomboidal-shaped ring-plain, 12 miles in diameter, standing in an isolated position on the Mare Imbrium between Lambert and Gay-Lussac.  Its bright walls, rising about 2500 feet above the Mare, are much terraced within, especially on the E. There is a bright little crater on the N. outer slope, with a short serpentine ridge running up to it from the region S. of Lambert, and another winding ridge extending from the S. wall to the E. of two conspicuous craters, standing about midway between Pytheas and Gay-Lussac.  The former bears a great resemblance to the ridge N. of Madler, and, like this, appears to traverse the N. border.  The interior of Pytheas, which is depressed more than 2000 feet below the Mare, includes a brilliant central peak.

LAMBERT.—­A ring-plain, 17 miles in diameter, presenting many noteworthy features.  The crest of its border stands about 2000 feet above the Mare Imbrium, and more than double this height above the interior.  The wall is prominently terraced both within and without; the outer slope on the W. exhibiting at sunrise a nearly continuous valley running round it.  When near the morning terminator, the region on the N. is seen to be traversed by some very remarkable ridges and markings; one cutting across the N. wall appears to represent a “fault.”  On the S. is a large polygonal enclosure formed by low ridges.  On the W., towards Timocharis, is a brilliant mountain 3000 feet high, a beautiful little object under a low sun.

LEVERRIER.—­The more westerly of a pair of little ring-plains on the N. side of the Mare Imbrium, and S.W. of the Laplace promontory.  It is about 10 miles in diameter, with walls rising some 1500 feet above the Mare, and more than 6000 feet above the interior, which seems to be without a central mountain or other features.  Schmidt shows the crater on the N. rim and another on the S.E. slope, both of which are omitted by Neison, though they are easy objects when Helicon is on the morning terminator.  About 20 miles on the S.E. there is a very bright little crater on a faint light area.

HELICON.—­The companion ring-plain on the E. It is 13 miles in diameter, and is very similar, though not quite so deep.  There is a crater on the S.E. wall, and, according to Neison, another on the outer slope of the N. border.  Webb records a central crater.  If Helicon is observed when on the morning terminator, it will be seen to be traversed by a curved ridge which cuts through the walls, and runs up to a bright crater S.E. of Leverrier.  It appears to be a “fault,” whose “downthrow,” though slight, is clearly indicated by an area of lower ground on the E. There is a great number of small craters in the neighbourhood of this formation.