ption is correct. Messier is also remarkable for the
light streak, often said to resemble a comet's tail, which extends from
the larger crater eastward to the shore of the _Mare Fecunditatis_.

Goclenius and Guttemberg, on the highland between the _Mare
Fecunditatis_ and the _Mare Nectaris_, are intersected and surrounded by
clefts, besides being remarkable for their broken and irregular though
lofty walls. Guttemberg is forty-five miles and Goclenius twenty-eight
miles in diameter. The short mountain range just east of Guttemberg, and
bordering a part of the _Mare Nectaris_ on the west, is called the
Pyrenees.

The _Mare Nectaris_, though offering in its appearance no explanation of
its toothsome name--perhaps it was regarded as the drinking cup of the
Olympian gods--is one of the most singular of the dark lunar plains in
its outlines. At the south it ends in a vast semicircular bay, sixty
miles across, which is evidently a half-submerged mountain ring. But
submerged by what? Not water, but perhaps a sea of lava which has now
solidified and forms the floor of the _Mare Nectaris_. The name of this
singular formation is Fracastorius. Elger has an interesting remark
about it.

"On the higher portion of the interior, near the center," he says, "is a
curious object consisting apparently of four light spots, arranged in a
square, with a craterlet in the middle, all of which undergo notable
changes of aspect under different phases."

Other writers also call attention to the fine markings, minute
craterlets, and apparently changeable spots on the floor of
Fracastorius.

We go now to the eastern side of the _Mare Nectaris_, where we find one
of the most stupendous formations in the lunar world, the great mountain
ring of Theophilus, noticeably regular in outline and perfect in the
completeness of its lofty wall. The circular interior, which contains in
the center a group of mountains, one of whose peaks is 6,000 feet high,
sinks 10,000 feet below the general level of the moon outside the wall!
One of the peaks on the western edge towers more than 18,000 feet above
the floor within, while several other peaks attain elevations of 15,000
to 16,000 feet. The diameter of the immense ring, from crest to crest of
the wall, is sixty-four miles. Theophilus is especially wonderful on the
fifth and sixth days of the moon, when the sun climbs its shining
pinnacles and slowly discloses the tremendous chasm that lies within its
circles