REGIOMONTANUS.—­A still more irregular walled-plain, of about the same area, closely associated with the S. flank of Purbach, having a rampart of a similar complex type, traversed by passes, longitudinal valleys, and other depressions.  Schmidt alone shows the especially fine example of a crater-row, which is not a difficult object, in connection with the S.E. wall.  Excepting one crater, nearly central, and some inconspicuous ridges, I have seen no detail on the floor.  Schmidt, however, records many features.

WALTER.—­A great rhomboidal walled-plain, 100 miles in diameter, with a considerably depressed floor, enclosed by a rampart of a very complex kind, crowned by numerous peaks, one of which, on the W., rises 10,000 feet above the interior.  If the formation is observed when it is close to the morning terminator, say, when the latter lies from l deg. to 2 deg.  E. of the centre of the floor, it is one of the most striking and beautiful objects which the lunar observer can scrutinize.  The inner slope of the border which abuts on Regiomontanus, examined at this phase under a high power, is seen to be pitted with an inconceivable number of minute craters; and the summit ridge, and the region towards Werner, scalloped in a very extraordinary way, the engrailing (to use an heraldic term) being due to the presence of a row of big depressions.  The floor at this phase is sufficiently illuminated to disclose some of its most noteworthy features.  Taking its area to be about 8000 square miles, at least 1200 square miles of it is occupied by the central mountain group and its adjuncts, the highest peak rising to a height of nearly 5000 feet (or nearly 600 feet higher than Ben Nevis), above the interior, and throwing a fine spire of shadow thereon.  In the midst of this central boss are two deep craters, one being about 10 miles in diameter, and a number of shallower depressions.  In association with the loftiest peak, I noted at 8 h., March 9, 1889, two brilliant little craters, which presumably are not far from the summit.  Near the E. corner of the floor there is another large deep crater, and, ranging in a line from the centre to the S.E. wall, three smaller craters.

LEXELL.—­On the E. of Walter extends an immense plain of irregular outline, which is at least equal to it in area.  Though no large formation is found thereon; many ridges, short crater-rows, and ordinary craters figure on its rugged superficies; and on its borders stand some very noteworthy objects, among them, on the S., the walled-plain Lexell, about 32 miles in diameter, which presents many points of interest.  Its irregular wall, rising, at one point on the S.W., to a height of nearly 8000 feet, is on the N.W. almost completely wanting, only very faint indications of its site being traceable, even under a low morning sun.  On the opposite side it is boldly terraced, and has a large crater on its summit.  The interior, the tone of which is conspicuously darker than that of the region outside, contains a small central hill, with two craters connected with it.  The low N.W. margin is traversed by a delicate valley, which, originating on the N. side of the great plain, crosses the W. quarter of Lexell and terminates apparently on the S.W. side of the floor.