s on the E. is especially noteworthy. The
central peak is not prominent, but close under it on the E. is a deep
fissure, extending from near the centre, and dying out before it reaches
the S. border. At the foot of the N.E. _glacis_ there are traces of a
ring with low walls.

THEON, SEN.--A brilliant little ring-plain, E.N.E. of Delambre, 11 miles
in diameter, and of great depth, with a regular and perfectly unbroken
wall. North of it is a bright little crater.

THEON, JUN.--A ring-plain similar in size and in other respects to the
last, situated about 23 miles S. of it on a somewhat dusky surface.
Between the pair is a curious oblong-shaped mountain mass; and on the E.
a long cliff (of no great altitude, but falling steeply on the E. side)
extending S. towards Taylor _a_. Just below the escarpment, I find a
brilliant little pair of craterlets, of which Neison only shows one.

ALFRAGANUS.--A large bright crater, about 9 miles in diameter, with very
steep walls, some distance S.S.W. of Delambre, and standing on the W.
edge of a large but very shallow and irregular depression W. of Taylor.
There is a remarkable chain of craters on the W. of it. Alfraganus is the
centre of a system of light streaks radiating in all directions, one ray
extending through Cyrillus to Fracastorius.

TAYLOR.--A deep spindle-shaped ring-plain, S. of Delambre, about 22 miles
in length. The wall appears to be everywhere continuous, except at the
extreme N. and S. ends, where there are small craters. The outer slopes,
both on the E. and W., are very broad and prominent, but apparently not
terraced. There is an inconspicuous central hill. On the W. is the
irregular enclosure, already referred to under Alfraganus. Three or four
short winding valleys traverse the N. edge of this formation, and descend
to the dark floor. On the N.E. is the remarkable ring-plain Taylor _a_,
18 miles in diameter, rising, at an almost isolated mountain mass on the
E. border, to a height of 7000 feet above the interior. The more regular
and W. section of this formation is not so lofty, and falls with a gentle
slope to the dark uneven floor, on which there is some detail in the
shape of small bright ridges and mounds. On the surface, N.W. of Taylor
_a_, is a curious linear row of bright little hills. Taylor and the
vicinity is better seen under low evening illumination than under morning
light.

HIPPARCHUS.--Except under a low sun, this immense walled-plain is by no
me