April 1, ISOG.] 



KNOWLEDGE 



85 



Plinius, a fine terraced'ring-plain some thirty-two miles in 

 diameter, whicb, on a smaller scale, bears much the same 

 relation to the chief "seas" in the western hemisphere 

 that the superb formation Copernicus does to those in the 

 eastern. Both, completely ramparted rings of especially 

 massive construction, appear to be strategically placed so 

 as to dominate the approach to the neighbouring plains ; 

 and Mr. Elger, in^his 

 recent and valuable 

 work on the Moon, 

 is led to speal; of 

 Pliny as reminding 

 him "of a great 

 fortress or redoubt 

 erected to command 

 the passage between 

 the Mare Tranquilli- 

 tatis and the Mare 

 Serenitatis." The 

 rampart of Pliny is 

 not, however, raised 

 to any great height 

 above the surround- 

 ing country, though 

 its highest point, 

 clearly seen on the 

 photograph on the 

 east wall of the ring, 

 rises some six thou- 

 sand four hundred 

 feet above the floor of 

 the interior ; which 

 is thus considerably 

 depressed below the 

 level of the general 

 surface in the 

 neighbourhood. The 

 floor of the interior 



words. The photograph does not, however, reach as far 

 as this innermost region, and. the dark grey margin is 

 alone shown. 



The only two other prominent features of the photo- 

 graph are the two smaller ring-plains Koss and Dawes, 

 which, following out the military metaphor, stand as 

 outworks of Plinius to prevent its being outflanked by an 



Key Map of Plinius and Curier and Licetus. 



is broken up by many hillocks, and two bright hUls of very 

 considerable height occupy the centre. They are distinctly 

 shown in the photograph. The southern side of the 

 wall slopes very gradually down to the plain outside, 

 forming an extended glacis some ten or twelve miles 

 broad. 



To the east of Pliny a bright mountainous region is 

 seen — the last ridges of the Haemus Mountains, one of the 

 four great ranges which shut in the Mare Serenitatis, and 

 render it the most sharply outlined of all the lunar man'a. 

 These mountains terminate in a great headland nearly 

 five thousand feet high, the Promontorium Acherusia, on 

 the northern slope of which four deep craters are very 

 plainly seen. 



North of Plinius a broad " riU " or cleft is seen on the 

 photograph, starting,' from amongst the Hsemus Mountains, 

 close under the southern slope of the great headland just 

 mentioned, and running ri^ht across the photograph to 

 Dawes, a bright ring-plain on the western edge of the 

 photograph. Further north lies a second cleft inclined 

 at a small angle to the first ; whilst between the two, but 

 not to be discerned on the photograph, is a thurd — faint, 

 small, and difficult. 



These rills mark the frontier line of the two great maria — 

 the more southern one. the "Tranquillity." standing at the 

 higher level of the two, a gentle slope descending from it 

 towards the " Serenity." In the latter, " deep calls to 

 deep," for within a broad grey margin, itself lower than 

 the "Tranquillity," lies an inner "Serenity," deeper 

 still, some eighty thousand square miles in area, which 

 full of a fine, clear, light-green tint " — in Neville's 



invader from the south. Dawes is remarkable for standing 

 on a broad circular platform of brighter material than the 

 surrounding country, a feature well shown in the photo- 

 graph. 



The new objects revealed by the photograph are neither 

 large nor numerous, for this is an attractive region to the 

 selenographer, and it has been well and frequently explored. 

 But Dr. Weinek claims that the following new features are 

 shown :— 



(a.) a double craterlet, shown as single and small by 

 Schmidt. 



(B.) A set of two, or perhaps three, interlaced craterlets. 



(c.) A small doubtful object, s. Plinius. 

 It is difficult, however, to bring out these minute details 

 in a photographic reproduction, which has itself been 

 copied from a copy from an enlargement. 



The right-hand photograph, with its mass of detail and 

 intricate structure, is a great contrast to the simplicity of 

 arrangement of the Plinius region. In Licetus we have 

 not one ring-plain, but four, which, by mutual encroachment 

 the one on the other, and the consequent partial destruction 

 of the boundary walls, have been fused into one very 

 irregular walled plain. The principal member of the group 

 is <(, the one to the north. It is some fifty miles in diameter, 

 and is nearly circular in its real shape (it is, of course, 

 seen somewhat foreshortened). The highest peak of the 

 wall rises nearly thirteen thousand feet above the interior. 

 The other chief object shown in the photograph is Cuvier, 

 a fine walled plain of about the same diameter as Licetus a, 

 and walls of about the same elevation. For the minor 

 objects in the field the photograph itself will give more 



