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TEE POPULAR SCIENCE MONTHLY. 



dence that the sun-spots are of the nature of depressions or openings 

 in the photosphere. Both Herschels claim to have observed a notch 

 in the sun's edge as a spot is disappearing ; and the order in which 

 the parts of a spot appear and disappear at the solar border is not 

 what it would be if the spot were even with the surface, but is just 

 what it would be if it were a rent or opening. 



The question before its is one of solar meteorology. Spectrum 

 analysis proves that matter exists upon the sun in a gaseous form. 

 The great mobility of its envelope, and the rapidity and extent of ita 

 changes, imply an atmosphere of extreme complexity, and probably of 

 great depth. The appearances of the solar atmosphere are believed to 



Fig. 4. 



hi 



Faculse to the Neighborhood of a Spot. (Chacornac.) 



be due to masses of the nature of clouds. But, while our clouds are 

 watery, or are formed by precipitated aqueous vapor, the solar clouds 

 are inferred to be more or less metallic, or to be composed of particles 

 of various metals and other substances in a state of intense heat. 

 Metallic vapors, at any rate, are proved to exist on the surface of the 

 sun. 



The first hypothesis of the solar constitution, which professed to 

 account for the spots, was put forth in the last century by a Scotch 

 astronomer, Alexander Wilson, and was accepted with modifications 

 by Bode and Herschel, and continued to prevail until within a few 

 years, being accepted by Arago. It was formed under the old an- 

 thropocentriv bias ; that is, the notion that man is the central object of 



