346 THE CHEMISTRY OF THE SUN. [CHAP. 



2. There are inversions of lines in the same elements in the 

 prominences as there are inversions in the spots, that is to say, 

 in certain prominences we see certain lines of a substance with- 

 out others ; in certain other prominences we see the other lines 

 without the first ones. 



3. Very few lines are strongly affected at once, as a rule, 

 and a very small proportion altogether; smaller than in the 

 case of spots. 



4. The prominences are not so subject as spots to sudden 

 changes so far as lines of the same element are concerned. 



5. There is a change in the lines affected according to the 

 sun-spot period. 



6. The lines of a substance seen in the prominences are 

 those which in our laboratories are observed to be consider- 

 ably brightened when we change the arc spectrum for the 

 spark spectrum. 



7. None of the iron lines ordinarily visible in prominences 

 are seen at the temperature of the oxy-hydrogen flame. Some 

 of the oxy-hydrogen flame-lines are seen in the spots, but, as 

 said before, none of these lines have ever been seen in the 

 prominences. 



8. A large number of lines ordinarily seen are of unknown 

 origin. 



9. Many of the lines seen are not ordinarily seen amongst 

 the Fraunhofer lines. Some are bright lines. 



10. As in the spots we found that the H and K lines of 

 calcium in the ultra-violet were always bright in the spot- 

 spectrum, the other lines of calcium and the other substances 

 being darkened and widened, so also it would appear that the 

 lines H and K of calcium are always bright in the prominences 

 in which the other lines of calcium are generally unaffected. 



11. Many of the lines are common to two or more elements 

 with the dispersion which has been employed. 



