Lunar Details. 371 



companion, 4800 ft. deep according to Schr., was discovered 

 by him, as well as a curious cleft running E.S.E. from it for 

 some distance, whicli he compared to the great valley in the 

 Alps, from the way in which its sloping sides are studded with 

 small irregular hills, as though an upheaved and hollow ridge 

 had fallen in, leaving the firmer portions hanging on its decli- 

 vities. In the Roman drawing, the end nest the crater is 

 feathered out into oblique lateral fissures. 



But the more remarkable features here are the great light- 

 streaks which diverge from it in every direction. They form a 

 less regular system of radiation than is to be found issuing 

 from other centres, but still their relation to Copernicus as a 

 departure point cannot be mistaken. Several of them connect 

 this great crater with others in the neighbourhood which repeat 

 the phenomenon, though on a smaller scale ; in fact, but few 

 large rings between the equator and 30° N. Lat. are wholly 

 without them, and some exhibit them even beyond that limit. 

 Near Copernicus they are merged in a bright but confused 

 "nimbus,^ or glory, interrupted here and there by streaks 

 and insulated patches of darkness, of which one is even found 

 close to the wall. Further out they expand, and direct them- 

 selves partly in divergent, partly in parallel lines, to the 

 neighbouring craters. Those pointing S. towards Ileinhold 

 (31) and Gainba,rt (a crater between Ileinhold and Sdmmer- 

 ing — Int. Obs., xii. 218) are more feeble and ill-defined; they 

 seem to indicate a fresh focus at Beinhold, but do not diverge 

 from it again : those directed towards Schroter are more con- 

 siderable, but do not reach the hill country; and here the 

 aspect of the surface is rather that of dark streaks traversing 

 brightness than the reverse. One such large dark streak 

 passes from Copernicus A to Stadius, the S. quarter of which 

 it includes, and then is lost. The darkest of these begin at a 

 grey mountain marked £, and extend S.W. for 40 miles : the in- 

 quiry of B. and M. whether one or other of the unascertained 

 spots of Eiccioli is to be recognized here, must appear singular 

 after a slight comparison of the old maps, which leave no doubt 

 of identification as to his Rhceticus, though some regret at its 

 not having been more accurately delineated in their great map. 

 Towards Eratosthenes almost all the light is united in one 

 mass, of which the brightness of the Sinus JEstuum may be 

 considered a continuation. Further N. begin some very pro- 

 minent streaks, few less than five miles broad, one leading to 

 Lambert (35), 14 miles ; some, which seem to start in the plain 

 itself, are crossed obliquely by others coming from Eratosthenes 

 the reverse way. Towards N. they are narrower and much in- 

 terrupted ; they are larger and more intense N.E. A great 

 divided streak passes from Mayer (32)— a large crater N.E. of 



