and thirty-five miles long by
eighty-four broad.

The _Mare Imbrium_, covering 340,000 square miles, is sparingly dotted
over with craters. All of the more conspicuous of them are indicated in
the chart. The smaller ones, like Caroline Herschel, Helicon, Leverrier,
Delisle, etc., vary from eight to twelve miles in diameter. Lambert is
seventeen miles in diameter, and Euler nineteen, while Timocharis is
twenty-three miles broad and 7,000 feet deep below its walls, which rise
only 3,000 feet above the surface of the _Mare_.

Toward the eastern border of the sea, south of the Harbinger Mountains,
we find a most remarkable object, the mountain ring, or crater plain,
called Aristarchus. This ring is not quite thirty miles in diameter, but
there is nothing on the moon that can compare with it in dazzling
brilliance. The central peak, 1,200 or 1,300 feet high, gleams like a
mountain of crusted snow, or as if it were composed of a mass of
fresh-broken white metal, or of compacted crystals. Part of the inner
slope of the east wall is equally brilliant. In fact, so much light is
poured out of the circumvallation that the eye is partially blinded, and
unable distinctly to see the details of the interior. No satisfactory
explanation of the extraordinary reflecting power of Aristarchus has
ever been offered. Its neighbor toward the east, Herodotus, is somewhat
smaller and not remarkably bright, but it derives great interest from
the fact that out of a breach in its northern wall issues a vast cleft,
or chasm, which winds away for nearly a hundred miles across the floor
of the _Mare_, making an abrupt turn when it reaches the foot of the
Harbinger Mountains.

The comparatively small crater, Lichtenberg, near the northeastern limb
of the moon, is interesting because Maedler used to see in its
neighborhood a pale-red tint which has not been noticed since his day.

Returning to the western side of the quadrant represented in Lunar Chart
No. 3, we see the broad and beautifully regular ringed plain of
Archimedes, fifty miles in diameter and 4,000 feet deep.

A number of clefts extend between the mountainous neighborhood of
Archimedes and the feet of the gigantic Apennine Mountains on the
southwest. The little double crater, Beer, between Archimedes and
Timocharis, is very bright.

The Apennines extend about four hundred and eighty miles in a
northwesterly and southeasterly direction. One of their peaks near the
southern end of the