60 LigJit and Colour of the Moon, 



opposition to the sun, and which, in fact, cannot even then be 

 perceived, except under very favourable circumstances. In truth, 

 we have doubts whether all eyes and all telescopes have the 

 capacity of perceiving them ; for, although their several limits 

 are sufficiently marked, the differences themselves are very 

 small. 



The great luminous bands also mentioned above, likewise 

 sometimes present a diversity of colour, when compared with 

 the brighter regions which surround them. They are some- 

 times distinctly seen to arise in certain parts of the surface 

 which are as clear and brilliant as themselves, and an attentive 

 examination makes it apparent that the bands are milk-white, 

 and the surrounding region is yellowish-white. It is true that 

 we have as yet determined this slight difference with certainty, 

 only in a few instances, particularly in those bands which ap- 

 pear to issue from Tycho towards the southern border. It 

 would be difficult to admit that the shining white of Aristar- 

 chus is any thing else than a very intense yellowish-white. 



It is, we apprehend, quite in vain to search for the cause of 

 these appearances. As to the different degrees of brightness, it is 

 evident that the different nature of the surface must, upon the 

 moon, as upon our globe, occasion various degrees of reflection. 

 We see, in truth, that upon our planet, independent of the differ- 

 ences of land and sea, the aspect of different portions of the 

 country when viewed from a distance is very different, and is 

 probably modified by the seasons. Respecting the shining 

 brightness of a great number of craters, it may be explained 

 by admitting, that through the influence of their large concavity, 

 they act as a mirror, and reflect a concentrated light towards 

 us. A confirmation of this explanation is to be found in the 

 fact that it is the eastern side which shines most before full 

 moon, and the western side after it ; and that the libration al- 

 so appears to have an analogous effect. Perhaps Aristarchus 

 is nothing else than the most perfect of all the reflecting sur- 

 faces, whence it enables us to perceive an image of the sun it- 

 self, or at least of a part of that luminary. At the same time 

 the phenomena are much too varied to be satisfactorily explain- 

 ed by this single circumstance alone, and there are among other 

 objects, mountains and portions of plains, which equal in splen- 



