PLATE XI. 



Low-level photograph, showing the dense caleiiim vapor lying ,iust above the 

 photosphere. In this i)hotogra|th very little of the pennnihra is eovered by the 

 caleinni vapor, but evidences may be seen, esi)ecially in the sonthern part t)f the 

 penumbra of the largest spot, of the eolumns of vapor which are greatly devel- 

 oped at the higher levels. 



156 



