190 PROCEEDINGS OP THE AMERICAN ACADEMY 



upon itself in two places, while at the same time it 

 became narrower. Fig. 6. At 12'' 45", it had reached 

 its former height ; and soon after, it sunk to a level 

 S with the chromosphere, and was lost in it. 

 flQc . At the same instant that the arc of hydrogen was 

 distended, it was seen projected on the spectrum op- 

 posite the sun, towards the violet. The figure of this protuberance 

 appeared exactly the same, whether it was projected on the spectrum 

 or seen between the wide-open jaws of tlie slit. However, when the 

 slit was narrow, the flame became invisible on the C line, although it 

 remained projected on the spectrum. When the protuberarice, after 

 having reached its greatest altitude, descended rapidly towards the 

 sun, it remained projected on the spectrum just as before, although 

 the descending motion was apparently in a contrary direction to the 

 ascending one ; but this did not seem to affect the position of the 

 flame on the spectrum. 



Cambridoe, Jan. 12, 1877. 



