IQO LIGHT SCIENCE FOR LEISURE HOURS. 



sphere must of course have ; but remembering how 

 much the inner portion of the coronal ring exceeds in 

 brightness the outer, it would seem that the illumina- 

 tion of the lunar disc must give us an exaggerated 

 measure of the true atmospheric effect. This illumi- 

 nation makes the edge of the moon only enough 

 brighter than the centre to give it the appearance of 

 a globe, but of almost inky blackness.' Dr. Balfour 

 Stewart, also, in a letter addressed to Mr. Brothers, 

 points out very clearly how insignificant relatively 

 must be the atmospheric illumination. * The light 

 which reaches us in a total eclipse from the centre of 

 the moon's disc, and which may be partly due to earth- 

 light reflected from the moon, may be safely taken as 

 somewhat exceeding that which can possibly be due to 

 atmospheric glare ; and inasmuch as in your photo- 

 graphs there is very little effect on the centre of the 

 moon's disc, I am led to think that very little of the 

 result obtained can be due to glare. I have here con- 

 fined myself strictly to your photographs, but the prin- 

 ciple laid down is applicable to all kinds of observations ; 

 and I must confess that I cannot at the present moment 

 see why the streamers, if they are caused by the atmo- 

 sphere, should invariably shoot outwards, and never 

 venture to trespass upon the moon's disc.' 



The present position [December 1871] of astro- 

 nomers is this. They have proved that there is a solar 

 appendage extending to a vast distance from the sun's ' 

 surface, radiated usually, if not always in structure, 

 and shining in great part with its own inherent lustre 



