of terrible precipices.

On the southeast Theophilus is connected by extensions of its walls with
a shattered ring of vast extent called Cyrillus; and south from
Cyrillus, and connected with the same system of broken walls, lies the
still larger ring named Catharina, whose half-ruined walls and numerous
crater pits present a fascinating spectacle as the shadows retreat
before the sunrise advancing across them. These three--Theophilus,
Cyrillus, and Catharina--constitute a scene of surpassing magnificence,
a glimpse of wonders in another world sufficient to satisfy the most
riotous imagination.

South of the _Mare Nectaris_ the huge ring mountain of Piccolomini
attracts attention, its massive walls surrounding a floor nearly sixty
miles across, and rising in some places to an altitude of nearly 15,000
feet. It should be understood that wherever the height of the mountain
wall of such a ring is mentioned, the reference level is that of the
interior plain or floor. The elevation, reckoned from the outer side, is
always very much less.

The entire region south and east of Theophilus and its great neighbors
is marvelously rough and broken. Approaching the center of the moon, we
find a system of ringed plains even greater in area than any of those we
have yet seen. Hipparchus is nearly a hundred miles long from north to
south, and nearly ninety miles broad from east to west. But its walls
have been destroyed to such an extent that, after all, it yields in
grandeur to a formation like Theophilus.

Albategnius is sixty-five miles across, with peaks from 10,000 to 15,000
feet in height. Sacrobosco is a confused mass of broken and distorted
walls. Aliacensis is remarkable for having a peak on the eastern side of
its wall which is more than 16,000 feet high. Werner, forty-five miles
in diameter, is interesting because under its northeastern wall Maedler,
some seventy years ago, saw a light spot of astonishing brightness,
unmatched in that respect by anything on the moon except the peak of
Aristarchus, which we shall see later. This spot seems afterward to have
lost brilliance, and the startling suggestion has been made that its
original brightness might have been due to its then recent deposit from
a little crater that lies in the midst of it. Walter is of gigantic
dimensions, about one hundred miles in diameter. Unlike the majority of
the ringed plains, it departs widely from a circle. Stoefler is yet
larger than Walter; but