runs out on to the plain near a large mountain just beyond the foot of the N. border.  In addition to the crater just mentioned, there are two smaller ones below the summit of the S. wall, and a small circular depression on the S.E. wall.  Mr. W.H.  Maw, F.R.A.S., has seen, with a 6 inch Cooke refractor, a bright marking at the N. extremity of the ring, which, when examined with a Dawes’ eyepiece, resembled an imperfect crater.  The floor includes at least four objects—­(1) A crater on the N.W., standing on a circular light area; (2) a white spot a little S. of the centre; (3) a smaller white spot S.E. of this; (4) another, near the inner foot of the S.W. wall.  Marius is an imposing object under oblique illumination, mainly because of the number of ridges by which it is surrounded.  I have frequently remarked at sunrise that the surface on the W., and especially the outer slope of the rampart, is of a decided brown or sepia tint, similar to that which has already been noticed with respect to Geminus and its vicinity, viewed under like conditions.  Schmidt in 1862 discovered a long serpentine cleft some distance N. of Marius, which has not been seen since.

ARISTARCHUS.—­The brightest object on the moon, forming with Herodotus (a companion ring-plain on the E.), and its remarkable surroundings, one of the most striking objects which the telescope has revealed on the visible surface, and one requiring much patient observation before its manifold details can be fully noted and duly appreciated.  Its border rises 2000 feet above the outer surface on the W., but towers to more than double this height above the glistening floor.  No lunar object of its moderate dimensions (it is only about 29 miles in diameter) has such conspicuously terraced walls, or a greater number of spurs and buttresses; which are especially prominent on the S. A valley runs round the outer slope of the W. wall, very similar to that found in a similar position round Marius.  There is also a distinct valley on the brilliant inner slope of the E. wall, below its crest.  It originates at a bright little crater, and is traceable round the greater portion of the declivity.  Under a moderately high sun, an oval area, nearly as large and fully as brilliant as the central mountain, is seen on this inner slope.  It is bordered on either side by bands of a duskier hue, which probably represent shallow transverse valleys.  From its dazzling brilliancy it is very difficult to observe the interior satisfactorily.  In addition, however, to the central mountain, there is a crater on the N.W. side of the floor.  On the S. side of Aristarchus is a large dusky ring some 10 miles in diameter, connected by ridges with the spurs from the wall, and on the S.E., close to the foot of the slope, is another smaller ring of a like kind.