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SCIENCE PROGRESS 



vapours constituting the umbra. This falling-in and heaping 

 together of the photospheric clouds to fill the partial void 

 formed by the ejection of the umbral vapours account for the 

 bright ring which is generally seen separating the umbra from 

 the penumbra. Around the sun-spot thus formed, but in an 

 upper level far above the reversing layer, circulate the hydrogen 

 flocculi, giving rise to the appearance of the solar vortices, 

 in which are generated by the friction of the various gyrating 

 vapours and gases electric currents with the accompanying 

 magnetic fields. 



