uth of the pole, is the _Mare Frigoris_, bordered on both sides by
uplands and mountains. At its southern edge we find the magnificent
Aristoteles, a mountain ring, sixty miles across, whose immense wall is
composed of terraces and ridges running up to lofty peaks, which rise
nearly 11,000 feet above the floor of the valley. About a hundred miles
south of Aristoteles is Eudoxus, another fine mountain ring, forty miles
in diameter, and quite as deep as its northern neighbor. These two make
a most striking spectacle.

We are now in the neighborhood of the greatest mountain chains on the
moon, the lunar Alps lying to the east and the lunar Caucasus to the
south of Aristoteles and Eudoxus, while still farther south, separated
from the Caucasus by a strait not more than a hundred miles broad,
begins the mighty range of the lunar Apennines. We first turn the
telescope on the Alps. As the line of sunrise runs directly across their
highest peaks, the effect is startling. The greatest elevations are
about 12,000 feet. The observer's eye is instantly caught by a great
valley, running like a furrow through the center of the mountain mass,
and about eighty or ninety miles in length. The sealike expanse south
and southeast of the Alps is the _Mare Imbrium_, and it is along the
coast of this so-called sea that the Alps attain their greatest height.
The valley, or gorge, above mentioned, appears to cut through the
loftiest mountains and to reach the "coast," although it is so narrowed
and broken among the greater peaks that its southern portion is almost
lost before it actually reaches the _Mare Imbrium_. Opening wider again
as it enters the _Mare_, it forms a deep bay among precipitous
mountains.

The Caucasus Mountains are not so lofty nor so precipitous as the Alps,
and consequently have less attraction for the observer. They border the
dark, oval plain of the _Mare Serenitatis_ on its northeastern side. The
great bay running out from the _Mare_ toward the northwest, between the
Caucasus and the huge mountain ring of Posidonius, bears the fanciful
name of _Lacus Somniorum_. In the old days when the moon was supposed to
be inhabited, those terrestrial godfathers, led by the astronomer
Riccioli, who were busy bestowing names upon the "seas" and mountains of
our patient satellite, may have pleased their imagination by picturing
this arm of the "Serene Sea" as a peculiarly romantic sheet of water,
amid whose magical influences the lun