Solar Eclipse. 295 



from behind the moon, at others to play along the margin, and 

 not unfrequently to dart in various directions, and to different 

 distances towards the centre of the moon's disc. 



Some time had elapsed before any indications of a general 

 law could be discovered to regulate these effects. It was at 

 length invariably observed, that wherever the inequalities of 

 the lunar circumference were most conspicuous, flashes of light 

 appeared to proceed most frequently from that quarter. Also, 

 that the greater the space in the darkened hemisphere, over 

 which they seemed to traverse, the more distinct they shewed, 

 and the nearer did their colour approximate, from a very dilute 

 purplish tint, to a red or dusky light. 



These two facts seem to afford an easy solution of the 

 phenomena in question. From the former it sufficiently ap- 

 pears that the primary cause is to be sought for in the in- 

 equalities of the moon's periphery. The solar rays, then, which 

 were intercepted by the circumference falling upon the declining 

 sides of the lunar mountains, would be variously reflected, not 

 merely from the angular direction of the incident rays, but also 

 as regards the position of the reflecting surfaces in relation to 

 the whole mass, — when reflected from the side directly exposed 

 to the sun, coruscations of thin light would appear to radiate 

 from behind the moon — as the reflecting point was situate 

 nearer the anterior surface, they would tend with proportional 

 inclinations, towards the interior of the disc. The second fact 

 is rather a necessary consequence, than a cause of these effects. 

 If these luminous streams or flashes proceeded from the re- 

 flection of the sun's light, it is obvious that the direction of the 

 reflected rays would materially influence their brightness. 

 When the path of the reflected rays traversed any considerable 

 portion of the moon's dark surface, they would produce a flash, 

 necessarily more brilliant than in a direction nearer the circum- 

 ference, both from the greater contrast of the surrounding 

 shade, and as being more remote from the splendour of the 

 sun's unobsoured segment. The greater the darkness, there- 

 fore, the more distinct they would appear; and hence they 

 differed in this respect, according to the different phases in 

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