YET A YEAR LATER. 89 



that our atmosphere is illuminated not merely in 

 directions lying close up to the moon's edge, but even 

 towards the body of the moon herself, by the light of 

 the coloured prominences and of the real solar corona. 

 The observer himself sees these luminous objects during 

 totality, and therefore the air all round him must be 

 illuminated by them. 1 



Now here a question of extreme delicacy arises. 

 The true solar corona undoubtedly grows fainter and 

 fainter with increased extension from the sun. That 

 is, if we could see the corona from some point raised 

 above the earth's atmosphere, so that no terrestrial 

 illumination could deceive us, we should see the corona 

 gradually diminishing in lustre with distance from the 

 sun, until at last it became too faint to be discerned 

 at all. On the contrary, the illumination of our at- 

 mosphere during totality must necessarily increase 

 with distance from the direction of the eclipsed sun. 



1 One cannot but be surprised at the stress which was laid by 

 some, soon after the eclipse of last December, on the fact that even 

 directly towards the moon's place, light was received which the spec- 

 troscope showed to be similar in character to that of the bright inner 

 portion of the corona. Not only was the fact dwelt on repeatedly as a 

 proof that the corona lies on our side of the moon, but it was com- 

 mended to my own special attention as a proof that I had been mistaken 

 in urging before the eclipse of 1870 that the corona is demonstrably a 

 solar appendage. In the very paper in which I urged this view before 

 the Royal Astronomical Society, on March 11, 1870, I pointed out that 

 our air must be illuminated towards the moon's place by the light of 

 all the visible solar appendages as the prominences, chromatosphere, 

 and corona as well as by reflected earth-light. My words were suf- 

 ficiently distinct. They ran as follows : ' The light from all these 

 sources should extend over the moon's disc, since it would illuminate 

 the air between the observer and the moon's body.' 



