n area of
more than 26,000 square miles, stand four craters, several little hills,
and light spots. On the W. is the much more regular and almost as large
formation, Otto Struve A, the W. border of Otto Struve forming its E.
wall. This enclosure is bounded elsewhere by a very low, broken, and
attenuated barrier. At sunrise the E. and W. walls, with the mountain
mass at the N. end, which they join, resemble a pair of partially-opened
calipers. There is one conspicuous little crater on the W. side of the
floor; and, at or near full moon, four or five white spots, nearly
central, are prominently visible.

BRIGGS.--This bright regular ring-plain, 33 miles in diameter, is
situated a short distance N. of Otto Struve A. A long ridge traverses the
interior from N. to S. On the E. is another large enclosure,
communicating with Otto Struve on the S., and really forming a N.
extension of this formation. It has a large and very deep crater, 12
miles in diameter, on its W. border.

LICHTENBERG.--A conspicuous little ring-plain, about 12 miles in
diameter, in an isolated position on the Mare, some distance N. of
Briggs. It was here that Madler records having occasionally noticed a
pale reddish tint, which, though often searched for, has not been
subsequently seen.

ULUGH BEIGH.--A good-sized ring-plain, E. of the last, with a bright
border and central mountain. Too near the limb for observation.

LAVOISIER.--A small bright walled-plain N. of Ulugh Beigh. It has a
somewhat dark interior. West of it is Lavoisier A, a ring-plain about 14
miles in diameter. Both are too near the limb for useful observation.

GERARD.--A large enclosure close to the limb, still farther N.,
containing a long ridge and a crater.

HARDING.--A small ring-plain W. of Gerard, remarkable for the peculiar
form of its shadow at sunrise, and for the ridges in its vicinity.

REPSOLD.--The largest of a group of walled enclosures, close to the limb,
on the E. side of the Sinus Roris.

XENOPHANES.--But for its position, this deep walled-plain, 185 miles in
diameter, would be a fine telescopic object, with its lofty walls, large
central mountain, and other details.

OENOPIDES.--A large and tolerably regular walled-plain, 43 miles in
diameter, on the W. of the last. The depressions on the W. wall are worth
examination at sunrise. There is apparently no detail whatever on the
floor.

CLEOSTRATUS.--A small ring-plain, N. of Xenophanes, surrounded by a
number of