The Lunar Eratosthenes and Copernicus. 277 



escaped attention. Of course, in any comparison of observa- 

 tions, a very close similarity of conditions would be required ; 

 but tliis being fulfilled, the non-appearance of the border would 

 so distinctly point to some unexplained and possibly unsuspected 

 cause, as to invest the inquiry with peculiar interest. Any 

 observer making an especial study of the edges of the interior 

 shadows of great craters might not regret the loss of time in 

 the end. 



The position of Eratosthenes is in the midst of landscapes 

 of very contrasted characters — the level Sinus jEstuum, the 

 towering Apennines, the vast extent of the Mare Imbrium, and 

 a most remarkable honey-combed district which we shall find 

 to the E. The line of the Apennines may be considered as 

 continued through it in that direction by a broken range of 

 hills, of which the extremity, of great steepness on every side, 

 especially N, — -the rj of B. and M., attains according to them 

 4000ft. : Schr. had given it 250ft. more. Running S. from the 

 E. side of the wall is a more considerable range, reaching near 

 its beginning, according to Schr., 9500ft., and leading down 

 to a large ring named Stadius by B. and M. when they failed 

 in identifying, as has been mentioned, Ricciolr's spot of that 

 name. This, 43 miles in diameter, and therefore surpassing in 

 that one respect its overpowering neighbour Eratosthenes, is a 

 strange contrast to it in other ways, the embankment, on which 

 they have figured two or three minute craters, being as a whole 

 scarcely 130ft. high, the mere outline of a wall, so as to have 

 escaped the attention of B. and M. for three years. Its sur- 

 face is not depressed, and the question may possibly suggest 

 itself, Have we here all that remains visible of a great ring, 

 whose height without and depth within have been subsequently 

 reduced to these trifling proportions by a circumfusion and 

 penetration of matter, once fluid or plastic, but now conso- 

 lidated ? The inquiry is thrown out as a mere suggestion for 

 examination and thought, with the sole addition that there are 

 very many other parts of the lunar surface where such a suspi- 

 cion might as naturally arise. B. andM. remark in its interior 

 only some ridges and one small crater, probably less elevated 

 even than the ring. Of this more hereafter. We next cross 

 the curious district already alluded to, and to be described at a 

 future time, to the magnificent Copernicus (30), one of the most 

 imposing and best-developed specimens of its class. There are 

 many its equals or superiors in size and depth in other parts of 

 the Moon, but few more remarkable at once in themselves and 

 their situation ; its structure is very perfect, and its insulated 

 position, and the absence of any material foreshortening, ex- 

 hibit it to especial advantage. The diameter of its colossal 

 wall is about 56 miles. This wonderful rampart, which does 



