PLAYFAIR.—­A ring-plain, 28 miles in diameter, with massive walls.  It is situated on the N. of Apianus, and is connected with it by a mountain arm.  The rampart is tolerably continuous, but varies considerably in altitude, rising on the S. to a height of more than 8000 feet above the interior.  On the E., extending towards Blanchinus, is a magnificent unnamed formation, bounded on the E. by a broad lofty rampart flanking Blanchinus, Lacaille, Delaunay, and Faye; and on the W. by Playfair and the mountain arm just mentioned.  It is fully 60 miles in length from N. to S. Sunrise on this region affords a fine spectacle to the observer with a large telescope.  The best phase is when the morning terminator intersects Aliacensis, as at this time the long jagged shadows of the E. wall of Playfair and of the mountain arm are very prominent on the smooth, greyish-blue surface of this immense enclosure.

PONTANUS.—­An irregular ring-plain, 28 miles in diameter, S.S.W. of Azophi, with a low broken border, interrupted on the S.W. by a smaller ring-plain, which forms one of a group extending towards the S.W.  The dark floor includes a central mountain.

ALIACENSIS.—­This ring-plain, 53 miles in diameter, with its neighbour Werner on the N.E., are beautiful telescopic objects under a low sun.  Its lofty terraced border rises at one peak on the E. to the tremendous height of 16,500 feet, and at another on the opposite side to nearly 12,000 feet above the floor.  The wall on the S. is broken by a crater, and on the W. traversed by narrow passes.  There is also a prominent crater on the inner slope of the N.E. wall.  The floor includes a small mountain, several little hills, and a crater.

WERNER.—­A ring-plain, 45 miles in diameter, with a massive rampart crowned by peaks almost as lofty as any on that of Aliacensis, and with terraces fully as conspicuous.  It has a magnificent central mountain, 4500 feet high.  At the foot of the N.E. wall Madler observed a small area, which he describes as rivalling the central peak of Aristarchus in brilliancy.  Webb, however, was unable to confirm this estimate, though he noted it as very bright, and saw a minute black pit and narrow ravine within it.  Neison subsequently found that the black pit is a crater-cone.  It would perhaps be rash, with our limited knowledge of minute lunar detail, to assert that Madler over-estimated the brightness of this area, which may have been due to a recent deposit round the orifice of the crater-cone.

POISSON.—­An irregular formation on the W. of Aliacensis, extending about 50 miles from W. to E., but much less in a meridional direction.  Its N. limits are marked by a number of overlapping ring-plains and craters, and it is much broken elsewhere by smaller depressions.  The E. wall is about 7000 feet in height.

GEMMA FRISIUS.—­A great composite walled-plain, 80 miles or more in length from N. to S., with a wall rising at one place nearly 14,000 feet above the floor.  It is broken on the N. by two fine ring-plains, each about 20 miles in diameter, and on the E. by a third open to the E. There is a central mountain, and several small craters on the floor, especially on the W. side.