274 The Lunar Eratosthenes and, Copernicus. 



slightest trace of a crater, as well as from its peculiarly level 

 character ; its smoothness being only broken by a few long but 

 very low ridges issuing from Eratosthenes (29). The compari- 

 son of this district with one swarming with minute craters a 

 little E. is extraordinary ; and these forms, which would have 

 been here most readily distinguishable, appear to be actually 

 wanting. It must, however, be observed that their predecessor, 

 Lohrmann, has delineated one very distinctly, of which, though 

 his work was before them, they have taken no notice ; and 

 Miidler subsequently (1841), when in charge of the great Dor- 

 pat achromatic, perceived several not laid down in the map. 

 Liz's crater I found very conspicuous with 5 \ inches, 1861, 

 April 18 and 20, May 17, as well as a second, and, perhaps, a 

 third. These inconsistencies, but too frequently to be met 

 with, introduce so much perplexity and obscurity into the 

 question of lunar change, that we look forward with interest 

 and pleasure to the survey now in progress under the auspices 

 of the British Association, the results of which will certainly 

 not be encumbered with similar ambiguities, at least on so 

 considerable a scale. 



Eratosthenes (29), a prominent crater, upwards of thirty- 

 seven miles in diameter, and, therefore, equal in area to some 

 of the smaller English counties, is, as our guides express it, 

 the mighty keystone of the Apennines, and probably (as they 

 think) the site of the outburst of that unknown violent agency 

 which raised the summits of Bradley and Hay gens. But for the 

 nearness of the still more imposing Copernicus (30), it would 

 certainly be the most remarkable feature of the neighbourhood. 

 It is, however, very inconspicuous in full illumination. A great 

 mountain occupies its centre, and the interior of the ring is 

 supported by strong, broad terraces ; the former, according to 

 Schr., divides into two branches, and the latter, on the E. side, 

 are in part separated by distinct ravines ; a fact which deserves 

 the attention of selenologists, as possibly throwing some light 

 on the mode of their formation. The ring 1 is brightest on E. 

 Here its summit lies 15,800ft. above the gulf, while on the oppo- 

 site side it only attains 10,900ft., that is, is only a little over- 

 topped by our Etna ! Schr. had given these measures consi- 

 derably less, and probably too small. Lohrmann mentions two 

 peaks, N.W. and >S.W., the former the point of junction of the 

 narrow prolongation of the Apennines ; E. of this point ho has 

 placed a small deep crater on the top of the wall, which B. 

 and M. have lowered to the inner terrace ; he also speaks of 

 several broad and generally parallel terraces descending as by 

 steps on the exterior, and extending furthest S. The height 

 of the wall from the outside is given by B. and M. as 3200ft. 

 W., 7400ft. E., showing, with as fair a degree of accordance as 



