Light and Colour of the Moon, 67 



from the annular zone of the mountain. The extremity near- 

 est this point, which is comparatively obscure, has 4° of bright- 

 ness (only 2° upon Aristarchus) ; the band then extends to 30, 

 50, and sometimes even 100, and 120 miles across the plains, 

 mountain-chains, isolated mountains, craters, fissures, and, in a 

 word, across every appearance which the moon presents, with- 

 out being in the slightest degree modified by any of them. 

 They are found in such numbers in the neighbourhood of the 

 annular mountain, which constitutes their centre, that they 

 form a kind of aureola or glory (nimbus) round it ; it is pecu- 

 liarly conspicuous round Kepler, and is scarcely visible round 

 Aristarchus. After this they ramify ; sometimes they are 

 somewhat curved, but not often ; they are connected by trans- 

 versal bands ; they are sometimes, too, somewhat interrupted 

 by portions where the light is more feeble, and sometimes, 

 towards their middle, there is only a dark ray for some ex- 

 tent. Often, instead of this radiated form, we notice two or 

 three, or a greater ijumber of rays which are perfectly paral- 

 lel. In some instances they terminate suddenly at a crater 

 or annular mountain ; they always remain distinctly visible at 

 full moon ; many of them approach the moon's edge, and there 

 lose themselves imperceptibly in the brightness of this part: 

 when this does not happen, most of them terminate insensibly in 

 a plain or mountain. The most extended of these radiated sys- 

 tems is that of Tycho. Here more than a hundred very distinct 

 luminous bands, some miles in breadth, project from it in all 

 points, and traverse nearly the whole of the south-west quadrant, 

 and a great part also of the south-east one. Two of these bands 

 extend, though unequally, from thence ; the one of them, which 

 is double, having a dark intermediate space, directs its course 

 in a north-easterly direction towards the Mare Nubium and 

 the Oceanus Procellarum, where it loses itself after a course of 

 about 150 miles. The other, simple and not so brilliant, tra- 

 verses nearly the whole visible surface of the moon, reaches, 

 still very feeble, to Menelaus, suddenly becomes clearer on 

 the dark Mare Serenitatis, divides it into two almost equal 

 halves, and probably advances still further towards the north, 

 till it is lost in the northern regions on the margin of the 

 disk ; it thus traverses 100° of a large circle of the moon, over an 



