PICARD.—­The largest of the craters on the surface of the Mare Crisium, 21 miles in diameter.  The floor, which includes a central mountain, is depressed about 2000 feet below the outer surface, and is surrounded by walls rising some 3000 feet above the Mare.  A small but lofty ring-plain, Picard E, on the E., near the border of the Mare, is remarkable for its change of aspect under different angles of illumination.  A long curved ridge running S. from this, with a lower ridge on the west, sometimes resemble a large enclosure with a central mountain.  Still farther S., there is another bright deep crater, a, with a large low ring adjoining it on the S., abutting on the S.E. border of the Mare.  Schroter bestowed much attention on these and other formations on the Mare Crisium, and attributed certain changes which he observed to a lunar atmosphere.

PEIRCE.—­This formation, smaller than Picard, is also prominent, its border being very bright.  There is a central peak, which, though not an easy object, I once glimpsed with a 4 inch Cook achromatic, and have seen it two or three times since with an 8 1/2 inch Calver reflector.  A small crater, detected by Schmidt, which I once saw very distinctly under evening illumination, stands on the floor at the foot of the W. wall.  Peirce A, a deeper formation, lies a little N. of Peirce, and has also, according to Neison, a very slight central hill, which is only just perceptible under the most favourable conditions.  Schmidt appears to have overlooked it.

PROCLUS.—­One of the most brilliant objects on the moon’s visible surface, and hence extremely difficult to observe satisfactorily.  It is about 18 miles in diameter, with very steep walls, and, according to Schmidt, has a small crater on its east border, where Madler shows a break.  It is questionable whether there is a central mountain.  It is the centre of a number of radiating light streaks which partly traverse the Mare Crisium, and with those emanating from Picard, Peirce, and other objects thereon, form a very complicated system.

MACROBIUS.—­This, with a companion ring on the W., is a very beautiful object under a low sun.  It is 42 miles in diameter, and is encircled by a bright, regular, but complex border, some 13,000 feet in height above the floor.  Its crest is broken on the E. by a large brilliant crater, and its continuity is interrupted on the N. by a formation resembling a large double crater, which is associated with a number of low rounded banks and ridges extending some distance towards the N.W., and breaking the continuity of the glacis.  The W. wall is much terraced, and on the N.W. includes a row of prominent depressions, well seen when the interior is about half illuminated under a rising sun.  The central mountain is of the compound type, but not at all prominent.  The companion ring, Macrobius C, is terraced internally on the W., and the continuity of its N. border broken by two depressions.  There is a rill-valley between its N.E. side and Macrobius.