TYCHO.—­As the centre from which the principal bright ray-system of the moon radiates, and the most conspicuous object in the southern hemisphere, this noble ring-plain may justly claim the pre-eminent title of “the Metropolitan crater.”  It is more than 54 miles in diameter, and its massive border, everywhere traversed by terraces and variegated by depressions within and without, is surmounted by peaks rising both on the E. and W. to a height of about 17,000 feet above the bright interior, on which stands a magnificent central mountain at least 5000 feet in altitude.  Were it not somewhat foreshortened, Tycho would be seen to deviate considerably from what is deemed to be the normal shape.  On the S. and W. especially, the wall approximates to the linear type, no signs of curvature being apparent where these sections meet.  The crest on the S. and S.E. exhibits many breaks and irregularities; and it is through a narrow gap on the S. that a rill-like valley, originating at a small depression near the foot of the S.W. glacis, passes, and, descending the inner slope of the S.E. wall obliquely, terminates near its foot.  There is a distinct crater on the summit ridge on the S.E., and another below the crest on the outer S.W. slope.  On the S. inner slope I have often remarked a number of bright oval objects, which, for the lack of a better word, may be termed “mounds” though they represent masses of material many miles in length and breadth.  The outer slope of Tycho, exhibiting under a high light a grey nimbus encircling the wall, includes—­craters, crater-pits, shallow valleys, spurs and buttresses—­in short, almost every variety of lunar feature is represented.  Excepting the central mountain and a crater on the W. of it, I have not seen any object on the floor, which, for some unexplained reason, is never very distinct.  Schmidt shows several low ridges on the N.E. side.  In a paper recently published in the Astronomische Nachrichten, Professor W.H.  Pickering, describing his observations of the Tycho streaks made at Arequipa, Peru, with a 13 inch achromatic, asserts that they do not radiate from the centre of Tycho, but from a multitude of minute craters on its S.E. or N. rim. (See Introduction.)

MAGINUS.—­An immense partially ruined enclosure, at least 100 miles from side to side, on the S.W. of Tycho, from which it is separated by a region covered with a confused mass of ring-plains and craters.  On almost every part of its broken border stand large ring-plains, many of which, if they were isolated, or situated in a less disturbed region, would rank as objects of importance; but among such a multitude of features they pass unnoticed.  The largest of them occupies no inconsiderable part of the S.E. wall, and is quite 30 miles in diameter, its own border being also much broken by depressions, as, indeed, are those of almost all the six or more large ring-plains which define the N. limits of Maginus.  The loftiest portion of what remains of a true border rises at one place to more than 14,000 feet.  On the floor, which is traversed by some of the Tycho rays, there is a mountain group associated with a crater, nearly central, and several large rings on the N. side.  Though the formation is very difficult to detect under a high sun, Madler’s dictum that “the full moon knows no Maginus” is not strictly true.