L. Trouvelot— Veiled Solar Spots. 175 



If there are breaks in the photosphere at many points of the 

 surface of the sun, it becomes easy to account for the unusual 

 thinness of the chromosphere this year, because as observed by 

 myself and others, at certain phases of the spots, the chromo- 

 spheric gases, rushing with impetuosity into the umbra, go 

 down under the photosphere like gigantic waterfalls, diminish- 

 ing consequently the thickness of the chromosphere. That 

 this takes place I shall give ample proof in another communica- 



It seems evident that the chromosphere near a spot is kept 

 from falling into the opening by a force from the interior. As 

 soon as this force decreases in energy, immediately the chro- 

 mosphere tends to cover it, and even to precipitate itself 

 through the opening when this force becomes extinct The 

 observations show this plainly. 



^ When a spot is decreasing, it is quite common to observe 

 ■'""'^ i-u- ujQ}jj.g^ g^^(j penumbra a " ' 



through a heavy fall of snow, their surfaces hein 



penum 



ing c 



nded 



of bluish fog. Id a few instances of very rare definition, I have 

 been surprised to see faint traces of this flocculent appearance 

 upon almost all the spots ; indeed it would seem that the spots 

 are rarely free from some faint traces of the chromospheric 

 gases. Probably the bright flocculent objects observed upon 

 the umbra and penumbra of spots, are the granulations of 

 the chromosphere dissolved to a greater or less degree by the 

 forces emanating from the spots. 



Perhaps it may not be idle to remark that, during the period 

 mentioned, I have almost every day observed small groups of 

 faculae in the polar regions, especially near the north pole of 

 the sun ; while, for the most part, they have been entirely 

 absent from the equatorial regions, where they are commonly 

 found. 



To conclude, my observations show : 



1. That during this year, and especially during the interval 

 from June 1 to August 18, and to a less degree to September 

 14, the chromosphere has been notably thinner than usual upon 

 the entire surface of the sun. 



2. That the granulations have been smaller and less nu- 

 merous. 



3. That the light-gray colored background seen between the 

 granules has been more conspicuous and has occupied more 

 space than usual. 



4. That there are spots, which I have named *' veiled spots," 

 which are seen through the chromosphere which is spread over 

 them like a veil. 



5. That these veiled spots are true openings of the photo- 

 sphere, like those of the ordinary spots. 



