B70 



THE ILLUMINATION OF THE ECLIPSED MOON. 



vvrhich have undergone a less degree of refraction than those 

 which strike the centre of the given section. Being rays 

 which have undergone a less degree of refraction, they must 

 bo rays which have passed through a liigher and more 

 transparent atmosphere, and therefore they will be brighter 

 rays. Deviation from the centre of the shadow is, in fact, in 

 this respect, equivalent to increased distance from the earth ; 

 and just as the eclipsed moon in apogee should in theory be 

 brighter than the eclipsed moon in perigee, so, it might be 

 thought, should the parts of the moon nearer the edge of the 

 shadow bo brighter than those nearer the centre. I have 

 no doubt that to an observer on the moon near the edge of 

 the shadow the luminous ring surrounding the earth would, 

 from the causes I have explained, be specially bright in the 

 part corresponding to his own position. But it does not 

 seem to follow that the region of the moon occupied by the 

 observer would be specially illuminated in consequence ; for 

 while the part of the luminous ring corresponding to his 

 position would be increased in. brightness, every other part 

 of the luminous ring as seen by him would be proportion- 

 ately diminished in brightness by reason of the rays wliicli 

 would reach him from those parts being necessarily more 

 refracted rays, and therefore rays which had passed through 

 a denser and less transparent medium. Thus it seems very 

 doubtful whether the total amount of refracted solar light 

 falling upon an object just within the shadow would be at all 

 greater than the amount falling upon an object near the 

 centre of the shadow in the same transverse section. 



Driven, therefore, to look for another explanation of the 

 increase of light towards the edge of the shadow, I am 

 disposed to seek it in the solar corona. Whatever diffi- 

 culties there may be in admitting tliat the light of the 

 corona can sensibly illiiuiinate an olijoct deep in the earth's 



