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THE POPULAR SCIENCE MONTHLY. 



pear as an opaque layer the umbras of spots. A cloud once formed 

 in this manner acts as a screen toward the higher regions ; hence a 

 secondary cooling effect in those regions also, and the formation oi 

 another cloudy layer, less dense the penumbra. 



Fig. 5. 



The speculations of M. Faye upon this subject have also attracted 

 some attention. He assumes the sun to be still in a gaseous state. 

 The photosphere he regards as consisting of clouds which are the sim- 

 ple consequence of cooling, and looks upon it, in fact, as the limit which 



