OF ARTS AND SCIENCES. 



187 



XII 



SUDDEN EXTINCTION OF THE LIGHT OF A SOLAR 

 PROTUBERANCE. 



By L. Trouvelot. 



Presented Nov. 14, 1877. 



On the 26th of June, 1874, while making my 

 daily observation of the sun with the spectro- 

 scope at the Harvard College Observatory, I saw 

 an unusual phenomenon, which may be worth re- 

 cording. The narrow slit of the instrument was 

 directed on the preceding side, about 270°, just 

 above a group of spots which was then very near 

 the limb, when I saw a brilliant protuberance 

 partly projected on the spectrum, on the side of 

 the rays of less refrangibility. In shape, this 

 hydrogen flame resembled an elongated comma, 

 having its acute extremity directed towards the 

 sun, where it terminated just a little above the 

 chromosphere. The chromosphere under this pro- 

 tuberance formed several slender and acute aigrette- 

 shaped flames, none of which, however, reached it. 

 The large prominence, which was slightly inclined to 

 the limb, had a height of 3' 37", and about 3° in its 

 greatest width. Fig. 1. 



When the slit was set wide open, so as to allow 

 the whole protuberance to be seen between its jaws, 

 the comma-shaped flame appeared perfect, and showed 

 plainly its texture. But, when it was observed with 

 a narrower slit, it became partly invisible on the C 

 line ; only a short and jagged portion being seen in 

 it, on the red side. Fig. 2. "When the slit was 

 carried along the protuberance by means of its 



FtG 



Red. 



FIG. 2 



