368 M. F. Zollner on the Spectral Analysis of the Stars. 



the alcohol-flame was just bounded by the rectangular slit, I 

 was surprised by the far greater beauty and distinctness with 

 which the images of the flame stood out from the diffusely 

 illuminated spectrum-ground. 



I may remark that I used in this experiment only 'one of the 

 above-mentioned newer prisms ; but it is clear that, with increa- 

 sing dispersion, the enfeeblement of the superposed non-homo- 

 geneous light may be enhanced at pleasure. 



In principle no difficulties prevent the application of this me- 

 thod to the sun's protuberances*. Yet practical success, with the 

 given ratio of the intensities of homogeneous protuberance- and 

 superposed atmospheric light, is essentially dependent on whether 

 a sufficiently strong dispersion for this ratio can be attained. If, 

 however, from the intensity and distinctness with which the lines 

 of the protuberances appear, especially the middle one (of which 

 I have convinced myself by my own observation at the Berlin 

 Observatory on the 24th of last December), it is allowable to 

 infer a very considerable relative brightness of the protuberances, 

 the means now at my disposal (four excellent systems of prisms) 

 will probably be sufficient to solve satisfactorily, in the way here 

 proposed, the problem of the visibility of protuberances. 

 Leipzig, February 1869. 



Appendix. 



M. Faye, after giving an account to the Academy of Sciences, 

 on September 20, of the above paper, proceeds as follows : — 



" M. Zollner has subsequently applied his new method to the 

 sun with the most complete success. He has been able to follow 

 and map from minute to minute with surprising facility and ac- 

 curacy the magnificent phenomena of the chromosphere ; he is 

 even about to photograph them, utilizing the images due to the 

 ray situated in the most photogenic part of the spectrum. 



" Some of the drawings above mentioned have been published 

 by Zollner in a separate pamphlet. They show clearly that the 

 protuberances are violent eruptions (Mr. Lockyer has already 

 approximately determined their velocity), and not clouds sus- 

 pended in an atmosphere. They might be said to consist of a 

 gaseous mass projected vertically into an almost vacuous space, 

 expanding almost immediately, and then falling more slowly, 

 assuming the most capricious forms. Perhaps in this way we 

 shall be able to group the new manifestations of the force which 

 the sun exerts upon the very light material of comets, — a polar 

 force, according to Bessel and Olbers, like electricity and mag- 

 netism; a force merely repulsive according to another hypothesis, 



* Owing to my not having yet completely set up the necessary instru- 

 ments, I have been unable actually to test this method. 



