The Sun 



of several bright lines, agree with the hypothesis, 

 already stated, of the gaseous state of the solar 

 nucleus. We are compelled to be satisfied with 

 these vague conjectures. 



It is, however, possible to obtain more 

 reliable information by turning our attention 

 to another point. As already pointed out the 

 sun is less luminous at the periphery than at the 

 centre ; this fact escapes every-day observation, 

 because the excessive radiance of the sun 

 deprives our retina of its sensibility, but it is 

 manifested both by photography and by photo- 

 metric comparisons made on a sufficiently 

 enlarged image of the sun. In this manner 

 the centre of the solar disc proves to be five times 

 more luminous than the periphery ; moreover, the 

 colour of the edge of the orb is distinctly reddish. 

 Peculiarities of this kind would be inexplicable 

 if the sun were limited to its photosphere; they 

 can only be explained by the existence of an 

 absorptive atmosphere, which diminishes in a 

 greater measure the rays emanating obliquely 

 from the edge of the orb than those originating 

 in the central regions. On the contrary, the 

 moon, which has no atmosphere, appears to us 



175 



