a considerable distance S.E. of it, encloses a wide and comparatively level area which is crossed by two short clefts.  The central mountains of Petavius, rising at one peak to a height of nearly 6000 feet above the floor, form a noble group, exceeding in height those in Gassendi by more than 2000 feet.  The convexity of the interior is such that the centre of it is about 800 feet higher than the margin, under the walls; a protuberance which would, nevertheless, be scarcely remarked in situ, as it represents no steeper gradient than about 1 in 300 on any portion of its superficies.  The great cleft, extending from the central mountains to the S.E. wall, and perhaps beyond, was discovered by Schroter on September 16, 1788, and can be seen in a 2 inch achromatic.  In larger instruments it is found to be in places bordered by raised banks.

WROTTESLEY.—­A formation, about 25 miles in diameter, closely associated with the E. wall of Petavius, the shape of which it has clearly modified.  Its border on the E., of the linear type, rises nearly 9000 feet above a light interior, where there is a small bright central mountain and some mounds.  There is a prominent valley running along the inner slope of the W. wall.

PALITZSCH.—­If this extraordinary formation is observed when the moon is about three days old, it resembles a great trough, or deep elongated gorge flanking the W. wall of Petavius, though it is a true ring-plain, albeit of a very abnormal type, about 60 miles in length and 20 miles in breadth, with a somewhat dusky interior.  On the outer slope of its W. wall is a bright ring-plain with a lofty border and a central mountain.

HASE.—­An irregular formation, about 50 miles in diameter, on the S.W. of Petavius, with which it is connected by extensions of the W. and E. walls of the latter.  Its rampart, some 7000 feet above the floor, is broken by depressions on the W.; and on the S. is bounded by a smaller ring-plain with still loftier walls.  Schmidt shows a large crater and three smaller ones on the W. side of the floor.

MARINUS.—­A ring-plain on the N.E. side of the Mare Australe, between Furnerius and the limb.

FURNERIUS.—­The fourth and most southerly component of the great meridional chain of walled-plains, commencing on the N. with Langrenus:  a fine but irregular enclosure, about 80 miles in extreme length and much more in breadth.  Its rampart is very lofty, and tolerably continuous on the N. and W., but on the other sides is interrupted by small craters and depressions.  At peaks on the E. it attains a height of more than 11,000 feet above the interior, and there are other peaks rising nearly as high.  There is a ring-plain (Furnerius B) with a central hill, on the E. side of the floor, and numerous craters and crater-pits in other parts of it.  On the N.W. side of B there is a short cleft, on the W., a well-marked crater-row, and on the E. a long rill-valley.  The very brilliant crater (Furnerius A) on the N.E. glacis is the origin of two fine light streaks, one extending S. for more than 100 miles, and the other in the opposite direction for a great distance.