er on the E. and exhibits
a gap. There is a central hill, only visible under a low sun. About
midway between Wollaston and this enclosure stands a small isolated
triangular mountain. From a hill on the E. runs a rill valley to the more
westerly of a pair of craters, connected by a ridge, on the S.E. of
Wollaston B.

MAIRAN.--A bright ring-plain of irregular shape, 25 miles in diameter, on
the E. of the Heraclides promontory. The border, especially on the E.,
varies considerably in altitude, as is evident from its shadow at
sunrise; at one peak on the W. it is said to attain a height of more than
15,000 feet above the interior. There is a very minute crater on the
crest of the S. wall, down the inner slope of which runs a rill-like
valley. About halfway down the inner face of the E. wall are two other
small craters, connected together by a winding valley. These features may
be seen under morning illumination, when about one-fourth of the floor is
in sunlight. Schroter is the only selenographer who gives Mairan a
central mountain. In this he is right. I have seen without difficulty on
several occasions a low hill near the centre. The formation is surrounded
by a number of conspicuous craters and crater-pits. On the N. there is a
short rill-like valley, and another, much coarser, on the S.

SHARP.--A ring-plain somewhat smaller than the last, on the E. of the
Sinus Iridum, from the coast-line of which it is separated by lofty
mountains. There is a distinct crater at the foot of its N.E. wall, and a
bright central mountain on the floor. On the N. is a prominent enclosure,
nearly as large as Sharp itself; and on the N.E. a brilliant little ring-
plain, A, about 8 miles in diameter, connected with Sharp, as Madler
shows, by a wide valley.

LOUVILLE.--A triangular-shaped formation on the E. of a line joining
Mairan and Sharp. It is hemmed in by mountains, one of which towers 5000
feet above its dusky floor.

FOUCAULT.--A bright deep ring-plain, about 10 miles in diameter, lying E.
of the mountains fringing the Sinus Iridum, between Bianchini and
Harpalus. A very lofty peak rises near its N. border, and, according to
Neison, it has a distinct central mountain, though neither Madler or
Schmidt show any detail within.

HARPALUS.--A conspicuous ring-plain, about 14 miles in diameter, on the
N.E. of the last, with a floor sinking 13,000 feet below the surrounding
surface. As the cubic contents of the border and _glacis_ are qu