388 COSMOS. 



intensity of the very oblique rays in their passage through 

 the rare media of the gas, nor does their emergence at the 

 surface and their transition into a different medium cause 

 polarization by refraction. Now, since the Sun does not 

 either exhibit any trace of polarization when the light is 

 suffered to reach the polariscope in a very oblique direction, 

 and at small angles from the margin, it follows from this 

 important comparison that the light shining in the Sun can- 

 not emanate from the solid solar body, nor from any liquid 

 substance, but must be derived from a gaseous, self-luminous 

 envelope. We thus possess a material physical analysis of 

 the photosphere. 



The same instrument has, however, also led to the con- 

 clusion that the intensity of the light of the Sun is not greater 

 in the centre of the disc than at its margins. When the two 

 complementary coloured images of the Sun the red and blue 

 are so arranged that the margin of the one image falls on 

 the centre of the other, perfect white will be produced. If 

 the intensity of the light were not the same in the different 

 parts of the Sun's disc, if, for example, the centre were more 

 luminous than the margin, then the partial covering of the 

 images in the common segments of the blue and red disc 

 would not exhibit a pure white, but a pale red, because the 

 blue rays would only be able to neutralize a portion of the 

 more numerous red rays. If, moreover, we remember that 

 in the gaseous photosphere of the Sun, in opposition to that 

 which occurs in solid or liquid bodies, the smallness of the 

 angle at which the rays of light emanate, does not cause 

 their number to diminish at the margins ; and as the same 

 angle of vision embraces a larger number of luminous points 

 at the margins than in the centre of the disc, we could not 

 here reckon upon that compensation which, were the Sun a 

 luminous iron globe, and consequently a solid body, would 

 take place between the opposite effects of the smallness of 



