SUN SPOTS AND EADIO STETSON 



217 



cycle progresses they increase in size and number and break out at 

 successively lower latitudes on the solar sphere, a given cycle of spots 

 finally disappearing just a few degrees from the solar equator. 



The true character of sun spots 

 as magnetic whirls in the solar 

 atmosphere was first established by 

 Hale, of the Mount Wilson Ob- 

 servatory, in 1908.^ By means of 

 the newly invented spectro-helio- 

 graph, Hale was able to photo- 

 graph different layers in the solar 

 atmosphere and establish the ex- 

 istence of vortices similar to the 

 whirlwinds which are character- 

 istic of cyclonic storms in the 

 earth's atmosphere. Furthermore 

 by analyzing with polarizing ap- 

 paratus the character of the rays 

 of light radiating from the sun 

 spots, Hale was able to demonstrate that the light emitted from the 

 center of these gigantic whirls betrayed unmistakably that they were 



Figure 2. — As the 11-year sun-spot 

 cycle waxes the latitude of the spots 

 decreases 



Figure 3. — Formation of a thunderstorm is analogous to the formation of 

 a sun spot. Note the vertical whirls about " High " and " Low " pres- 

 sure areas 



electromagnetic poles and that the doubling of the lines in the 

 spectrum over sun spots was due to the magnetic effect announced 

 by Zeeman in 1896. 



"Astrophys. Journ., vol. 28, p. 315, July to December, 1908. 



