370 Lunar Details. 



LUNAR DETAILS.— DOUBLE STARS.— CLUSTER AND 

 NEBULAE.— TRANSITS OF SATELLITES.— OCCULTA- 

 TIONS. 



BY THE EEV. T. W. WEBB, A.M., E.E.A.S. 



Much of the story of Copernicus remained untold when we 

 broke off last month, and what we have already heard may well 

 give us an interest in the remainder. It will be matter of 

 familiar observation how striking is its aspect under very 

 varied angles of illumination — how the magnificence of its 

 broad and massive wall, and the extraordinary roughness of 

 its glacis, as it rises upon the terminator, give place to a relief 

 in higher sunlight which exhibits the serpentine terraces, the 

 central elevations, and the whole arrangement of the structure 

 in a more intelligible manner ; and how this aspect is again 

 gradually replaced under increased illumination by one of more 

 delicate but still very expressive relief, and of considerable 

 permanency ; I have seen a little true shadow cast from the 

 great peak in the W. wall, and from a steep terrace on that 

 side, as late as' 3d. 1-^h. before Full Moon. The beauty of these 

 very dissimilar, yet intimately related aspects must be seen, 

 and studied, to be fully appreciated. Mention ought to be 

 made of a very striking engraving proceeding from the Collegio 

 Romano,* as exhibiting the latter of these positions on a large 

 scale, and with much cleverness of effect as well as fullness of 

 detail, but, we are obliged to add, some degree of inattention 

 also. We shall, however, proceed at present with an abstract 

 of the remarks of B. and M. on its immediate vicinity. It 

 is enclosed by a great mass of closely crowded mountain chains, 

 arranged in lines partly radiating, partly parallel to the ring, 

 especially on E. Here many of them are of very slight eleva- 

 tion (250 to 650 ft.), but on the opposite side they reach nearly 

 3000 ft. " Craters are first found at some distance, and but 

 few in the mountains themselves, though those very obvious ;" 

 a great contrast, by the way, to the aspect of many other largo 

 cavities and their rings, as though the eruptive action had here 

 more completely exhausted itself at one wide and unimpeded 

 aperture. One is a small twin-crater {Copernicus A) on the S. 

 slope, already seen by Schr., the larger orifice lying N., so 

 deep that it holds its shadow longer than the "Teat crater 

 itself; its ring, of 6 light, is much more distinct from its 

 interior of 3° than is usual in such little cavities ; the small 

 crater B, equidistant from the grand ring S.E., appears of 

 similar depth. Towards the foot of the N.E. glacis, a larger 

 opening, Gay Lussac, lias broken through ; this with its smaller 

 * Memoirs Roy. Astron. Society, XXXII. pi. viii. 



