similar objects, all too near the limb for observation.

PYTHAGORAS.--A noble walled-plain, 95 miles in diameter, which no one who
observes it fails to lament is not nearer the centre of the disc, as it
would then undoubtedly rank among the most imposing objects of its class.
Even under all the disadvantages of position, it is by far the most
striking formation in the neighbourhood. Its rampart rises, at one point
on the N., to a height of nearly 17,000 feet above the floor, on which
stands a magnificent central mountain, familiar to most observers.

THIRD QUADRANT

EAST LONGITUDE 0 deg. TO 20 deg.

MOSTING.--A very deep ring-plain, 15 miles in diameter, near the moon's
equator, and about 6 deg. E. of the first meridian. There is a crater on
the N. side of its otherwise unbroken bright border, an inconspicuous
central mountain, and, according to Neison, a dark spot on the S. side of
the floor. At some distance on the S.S.W., stands the bright crater,
Mosting A, one of the most brilliant objects on the moon's visible
surface.

REAUMUR.--A large pentagonal enclosure, about 30 miles in diameter, with
a greatly broken border, exhibiting many wide gaps, situated on the E.
side of the Sinus Medii, N.W. of Herschel. The walls are loftiest on the
S. and S.W., where several small craters are associated with them. A
ridge connects the formation with the great deep crater Reaumur A, and a
second large enclosure lying on the W. side of the well-known valley W.
of Herschel. At the end of a spur on the S. side of the great crater
originates a cleft, which I have often traced to the N.W. wall of
Ptolemaeus, and across the N. side of the floor of this formation to a
crater on the N.E. quarter of it, Ptolemaeus _d_. There is a short cleft
on the W. side of the floor of Reaumur, running from N. to S.

HERSCHEL.--A typical ring-plain, situated just outside the N. border of
Ptolemaeus, with a lofty wall rising nearly 10,000 feet above a somewhat
dusky floor, which includes a prominent central mountain. Its bright
border is clearly terraced both within and without, the terraces on the
inner slope of the W. wall being beautifully distinct even under a high
light, and on the outer slope are some curious irregular depressions. On
the S.S.E. is a large oblong deep crater, close to the rocky margin of
Ptolemaeus, and a little beyond the foot of the wall on the N.W. is a
smaller and more regular rimmed depression, _b_, standing near t