n 500 feet higher, with
many others nearly as lofty in the vicinity. Calippus has not apparently
a central peak or any other features on the floor.

CASSINI.--This remarkable ring-plain, about 36 miles in diameter, is very
similar in character to Posidonius. It has a very narrow wall, nowhere
more than 4000 feet in height, and falling on the E. to 1500 feet. Though
a prominent and beautiful object under a low sun, its attenuated border
and the tone of the floor, which scarcely differs from that of the
surrounding surface, render it difficult to trace under a high angle of
illumination, and perhaps accounts for the fact that it escaped the
notice of Hevel and Riccioli; though it is certainly strange 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 o