ibit
two or three breaks. The dark floor appears to be devoid of detail.
Schmidt, however, draws two large irregular mounds E. of the centre, and
shows four narrow light streaks crossing the interior nearly parallel to
the longer axis of the formation.

DE LA RUE.--Notwithstanding its great extent, this formation hardly
deserves a distinctive name, as from the lowness of its border it is
scarcely traceable in its entirety except under very oblique light.
Schmidt, nevertheless, draws it with very definite walls, and shows
several ridges and small rings in the interior. Among these objects, a
little E. of the centre, there is a prominent peak.

STRABO.--A small walled-plain, 32 miles in diameter, connected with the
N. border of the last.

THALES.--A bright formation, also associated with the N. side of De la
Rue, adjoining Strabo on the N.E. Schmidt shows a minute hill in the
interior.

There are several unnamed formations, large and small, between De la Rue
and the limb, some of which are well worthy of examination.

WEST LONGITUDE 40 deg. TO 20 deg.

MASKELYNE.--A regular ring-plain, 19 miles in diameter, standing almost
isolated in the Mare Tranquilitatis. The floor, which includes a central
mountain, is depressed some 3000 feet below the surrounding surface.
There are prominent terraces on the inner slope of the walls. Schmidt
shows no craters upon them, but Madler draws a small one on the E., the
existence of which I can confirm.

MANNERS.--A brilliant little ring-plain, 11 miles in diameter, on the
S.E. side of the Mare Tranquilitatis. There appears to be no detail
whatever in connection with its wall. It has a distinct central mountain.
About three diameters distant on the S.W. there is a bright crater,
omitted by Madler and Neison.

ARAGO.--A much larger formation, 18 miles in diameter, N. of the last,
with a small crater on its N. border, and exhibiting two or three spurs
from the wall on the opposite side. The inner slopes are terraced, and
there is a small central mountain. There are two curious circular
protuberances on the Mare E. of Arago, which are well seen when the W.
longitude of the morning terminator is about 19 deg., and a long cleft,
passing about midway between them, and extending from the foot of the E.
wall to a small crater on the edge of the Mare near Sosigenes. Another
cleft, also terminating at this crater, runs towards Arago and the more
northerly of the protuberances.

CAUCH