l mountain
towards the S.W. wall. They are all more or less difficult objects,
requiring exceptionally favourable weather and high powers. A fine
mountain range, the Percy Mountains, is connected with the E. flank of
Gassendi, extending in a S.E. direction towards Mersenius, and defining
the N.E. side of the Mare Humorum.

BULLIALDUS.--A noble object, 38 miles in diameter, forming with its
surroundings by far the most notable formation on the surface of the Mare
Nubium, and one of the most characteristic ring-plains on the moon. It
should be observed about the time when the morning terminator lies on the
W. border of the Mare Humorum, as at this phase the best view is obtained
of the two deep parallel terrace valleys which run round the bright inner
slope of the E. wall, of the crater-row against which they abut on the
S.E., and of the massive W. _glacis_, with its spurs and depressions. The
S. border of Bullialdus has been manifestly modified by the presence of
the great ring-plain A, a deep irregular formation with linear walls,
which is connected with it by a shallow valley. The rampart of Bullialdus
rises about 8000 feet above a concave floor, which sinks some 4000 feet
below the Mare on the E. With the exception of the fine compound central
mountain, 3000 feet high, there are few details in the interior. On the
S., is the fine ring-plain B, connected with the S.E. wall near the
crater-row by a well-marked valley, and nearly due E. of B is another, a
square-shaped enclosure, C, with a very lofty little mountain on the E.
side of it, and a crater on its S. wall. In addition to these features,
there are many ridges and surface inequalities, very prominent under
oblique illumination.

LUBINIEZKY.--A regular enclosure, about 23 miles in diameter, N.E. of
Bullialdus, with a low attenuated border, which is nowhere more than 1000
feet in height. It is tolerably continuous, except on the S., where there
are two or three breaks. Its level dark interior presents no details to
vary its monotony. Close under the N.W. wall is a small crater connected
with it by a ridge, and E. of this a very rugged area, traversed in every
direction by narrow shallow valleys, which are well worth looking at when
close to the morning terminator. A bright spur projects from the N. wall
of Lubiniezky.

KIES.--A somewhat similar formation, S. of Bullialdus, about 25 miles in
diameter, also encircled by a border of insignificant dimensions,
attain