58 Light and Colour of the Moon, 



extent of more than 400 miles. When these bands are much 

 extended, they so much surpass in brightness every other part, 

 during full moon, with the exception of the bright craters, that 

 nothing can be determined concerning the forms of the ground 

 or surface. 



These luminous bands are not elevations. When low moun- 

 tain ranges come in their track or neighbourhood, they follow 

 neither their course, nor their outline ; and still less do moun- 

 tains properly so called. The mountains and the bands may 

 rather be said to alternate with each other ; for, when the 

 mountains commence distinctly to appear, the bands disappear, 

 and conversely. The bands may be obscurely perceived in 

 some plains (as in Stofler and Meton) even with an oblique 

 illumination, after they have ceased to be visible in mountain- 

 ous regions ; but this never continues after the sun has set. 



It is true that the very distinct band which traverses the 

 Mare Serenitatis, is accompanied by low ramifications (Berga- 

 dern) which are parallel to it, and of which some parts traverse it. 

 But the band itself appears so completely on the level of the 

 uniform surface, that it always disappears in the neighbourhood 

 of the confines of the light. We have verified the disappear- 

 ance during six hours of observations made in a night which 

 was peculiarly favourable. On approaching the confines of the 

 light, the mountain ranges became more distinct, and generally 

 visible for the first time, while the bands disappeared from our 

 eyes without leaving a trace behind, which would not have 

 happened if they had possessed even one degree of inclination. 



Besides the principal radiated systems we have just been 

 considering, which, though they have some minor differences, 

 are nevertheless very similar to each other, we also discover 

 upon the moon's surface many of these appearances, which are 

 incomplete, and sometimes even solitary bands. Thus three 

 rise from Proclus, forming with each other almost equal angles, 

 of about 120°, two of which are obscure and difficult to re- 

 cognise, while the third is more distinct, and terminates in a 

 marked bifurcation. On the Mare Fecunditatis, we perceive 

 another appearance of this kind, which has precisely the ap- 

 pearance of a comet with a double tail. The nucleus is re- 

 presented by two neighbouring craters of equal size ; the rays 



