that a formation which is thrown into such strong
relief at sunrise and sunset should have been overlooked,
while others hardly more prominent at these times
have been drawn and described. The outline of
Cassini is clearly polygonal, being made up of several
rectilineal sections. The interior, nearly at
the same level as the outside country, includes a large
bright ring-plain, A, 9 miles in diameter and 2600
feet in depth, which has a good-sized crater on the
S. edge of a great bank which extends from the S.W.
side of this ring-plain to the wall. On the E.
side of the floor, close to the inner foot of the
border, is a bright deep crater about two-thirds
of the diameter of A, and between it and the latter
Brenner has seen three small hills. The outer
slope of Cassini includes much detail. On the
S.W. is a row of shallow depressions just below the
crest of the wall, and near the foot of the slope
is a large circular shallow depression associated
with a valley which runs partly round it. The
shape of the
glacis on the W. is especially
noteworthy, the S.W. and N.W. sides meeting at a slightly
acute angle at a point 10 or 12 miles W. of the summit
of the ring. On the outer E. slope is a curious
elongated depression, and on the N. slope two large
dusky rings, well shown by Schmidt, but omitted in
other maps. Most of these details are well within
the scope of moderate apertures. Perhaps the most
striking view of Cassini and its surroundings is obtained
when the morning terminator is on the central meridian.
ALEXANDER.—A large irregularly shaped plain,
at least 60 miles in longest diameter, enclosed by
the Caucasus Mountains. On the S.W. and N.W.
the border is lineal. It has a dark level floor
on which there is a great number of 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.