rd, lies a fine example of a ring mountain, rather
more than forty miles in diameter, and with peak-tipped walls which in
some places are 13,000 feet in height, as measured from the floor
within. This is Macrobius. There is an inconspicuous central mountain in
the ring.

North of the _Mare Crisium_, and northwest of Macrobius, we find a much
larger mountain ring, oblong in shape and nearly eighty miles in its
greatest diameter. It is named Cleomenes. The highest point on its wall
is about 10,000 feet above the interior. Near the northeast corner of
the wall yawns a huge and very deep crater, Tralles, while at the
northern end is another oblong crater mountain called Burckhardt.

From Cleomenes northward to the pole, or to the northern extremity of
the crescent, if our observations are made during new moon, the ground
appears broken with an immense number of ridges, craters, and mountain
rings, among which we may telescopically wander at will. One of the more
remarkable of these objects, which may be identified with the aid of
Lunar Chart No. 1, is the vast ringed plain near the edge of the disk,
named Gauss. It is more than a hundred and ten miles in diameter. Owing
to its situation, so far down the side of the lunar globe, it is
foreshortened into a long ellipse, although in reality it is nearly a
circle. A chain of mountains runs north and south across the interior
plain. Geminus, Berzelius, and Messala are other rings well worth
looking at. The remarkable pair called Atlas and Hercules demand more
than passing attention. The former is fifty-five and the latter
forty-six miles in diameter. Each sinks 11,000 feet below the summit of
the loftiest peak on its encircling wall. Both are full of interesting
detail sufficient to occupy the careful observer for many nights. The
broad ring bearing the name of Endymion is nearly eighty miles in
diameter, and has one peak 15,000 feet high. The interior plain is flat
and dark. Beyond Endymion on the edge of the disk is part of a gloomy
plain called the _Mare Humboltianum_.

After glancing at the crater-shaped mountains on the western and
southern border of the _Mare Crisium_, Alhazen, Hansen, Condorcet,
Firmicus, etc., we pass southward into the area covered in Lunar Chart
No. 2. The long dark plain south of the _Mare Crisium_ is the _Mare
Fecunditatis_, though why it should have been supposed to be
particularly fecund, or fertile, is by no means clear. On the western
border o