f low hills.

EUDOXUS.--A bright deep ring-plain, about 40 miles in diameter, in the
hilly region between the Mare Serenitatis and the Mare Frigoris, with a
border much broken by passes, and deviating considerably from
circularity. Its massive walls, rising more than 11,000 feet above the
floor on the W., and about 10,000 feet on the opposite side, are
prominently terraced, and include crater-rows in the intervening valleys,
while their outer slopes present a complicated system of spurs and
buttresses. There is a bright crater on the N. _glacis_, and some
distance beyond the wall on the N.W. is a small ring-plain, and on the
S.E. another, with a conspicuous crater between it and the wall. Neison
draws attention to an area of about 1400 square miles on the N.E. which
is covered with a great multitude of low hills. E. of Eudoxus are two
short crossed clefts, and on the N. a long cleft of considerable delicacy
running from N.E. to S.W. It was in connection with this formation that
Trouvelot, on February 20, 1877, when the terminator passed through
Aristillus and Alphonsus, saw a very narrow thread of light crossing the
S. part of the interior and extending from border to border. He noted
also similar appearances elsewhere, and termed them _Murs enigmatiques_.

ARISTOTELES.--A magnificent ring-plain, 60 miles in diameter, with a
complex border, surmounted by peaks, rising to nearly 11,000 feet above
the floor, one of which on the W., pertaining to a terrace, stands out as
a brilliant spot in the midst of shadow when the interior is filled with
shadow. The formation presents its most striking aspect at sunrise, when
the shadow of the W. wall just covers the floor, and the brilliant inner
slope of the E. wall with the little crater on its crest is fully
illuminated. At this phase the details of the terraces are seen to the
best advantage. The arrangement of the parallel ridges and rows of hills
on the N.E. and S.W. is likewise better seen at this time than under an
evening sun. A bright and deep ring-plain, about 10 miles in diameter,
with a distinct central mountain, is connected with the W. wall.

EGEDE.--A lozenge-shaped formation, about 18 miles from corner to corner,
bounded by walls scarcely more than 400 feet in height. It is
consequently only traceable under very oblique illumination.

THE GREAT ALPINE VALLEY.--A great wedge-shaped depression, cutting
through the Alps W. of Plato, from W.N.W. to E.S.E. It is more th