YET A YEAR LATER. 99 



We have only to remember, however, that the 

 moon looks so dark during totality as to seem perfectly 

 black, to see how very small a part atmospheric illumi- 

 nation can have in producing the coronal phenomena. 

 The light received from the direction of the moon's disc 

 must be at least as strong as any atmospheric illumina- 

 tion within the region occupied by the coronal glory ; 

 for this illumination, if we could see it alone, would 

 be nearly uniform, while, where the moon is, we re- 

 ceive ^(pver and above the atmospheric illumination) no 

 inconsiderable amount of what astronomers call earth- 

 light. The moon's surface, at the moment of a total 

 eclipse, is illuminated by the earth some twelve times 

 more brightly than the earth's surface in full moon- 

 light. If we look at a distant hill (not forest-covered) 

 bathed in the light of the full moon, we see that it is 

 appreciably luminous brighter certainly in appearance 

 than the dark-looking disc of the moon during an eclipse. 

 Yet the moon's disc, during eclipse, is twelve times 

 as luminous, at least ; and if all other light could be 

 removed, we should see the moon at that time as a disc 

 illuminated with no inconsiderable degree of brightness. 

 Since the moon actually looks almost black though 

 this reflected light is reinforced by the atmospheric 

 illumination we cannot but admit that the atmo- 

 spheric illumination alone must be very inconsiderable 

 compared with the light even of the outer parts of the 

 corona, which, though faint, seem by no means black. 



Professor Young, of America, has reasoned similarly 

 on this point. * Some influence,' he says, * our atmo- 



ii 2 



