The Sun 



to the chromosphere and the protuberances if 

 total eclipses of the sun had not realised before 

 our eyes a gigantic experiment. By interposing, 

 from time to time, the moon as a screen between 

 us and the sun's disc Nature protects us for a 

 moment against the radiance of the photosphere 

 and enables us to observe the zones surrounding 

 it. On such occasions the protuberances of the 

 chromosphere become visible to the naked eye, 

 but the light does not cease suddenly outside this 

 layer. A continuous and gradually- decreasing 

 glow extends around the sun to a greater thick- 

 ness than the diameter of the photosphere, 

 constituting what is called the corona. This 

 glow is not exactly concentric to the orb; it is 

 narrower in the polar regions and much broader 

 opposite the protuberances. Observed through 

 the spectroscope it gives a double spectrum, 

 formed, on one hand, by a continuous light 

 extending from red to blue, and on the other 

 by bright, separate lines. These lines prove the 

 corona to be self-luminous, and on examination 

 they prove the existence of various bodies, chief 

 amongst which is hydrogen. The continuous 



spectrum, on the other hand, proves the existence 



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