270 SCIENCE PROGRESS. 



on the north-east limb of the sun. The D 3 line was seen 

 very well, having every appearance of being double, with a 

 faint component on the red side, dimming away gradually ; 

 the line of demarcation between the components was not 

 well marked, but it was seen better in the prominence than 

 anywhere else on the limb " (" Observatory Note Book "). 



It became clear, then, that the middle of the chromo- 

 sphere line, as ordinarily seen, and as taken in the 

 comparison of 4th May, does not represent the place of 

 the brightest component of the double line, so that exact 

 coincidence was not to be expected. 



The circumstance that the line is double in both gas 

 and chromosphere spectrum, in each the less refrangible 

 component being the fainter, taken in conjunction with the 

 direct comparisons which have been made, rendered it 

 highly probable that one of the gases obtained from cleveite 

 is identical with that which produces the D 3 line in the 

 spectrum of the chromosphere. 



Other observers have since succeeded in resolving the 

 chromospheric line. On 20th June, Professor Hale found 

 the line to be clearly double in the spectrum of a promin- 

 ence, the less refrangible component being the fainter, and 

 the distance apart of the lines being measured as 0*357 

 tenth -metres (Ast. JVac/i., 3302). 



The doubling was noted with much less distinctness in 

 the spectrum of the chromosphere itself on 24th June. 

 Professor Hale points out that Rowland's value of the wave- 

 length (as well as that of 5875*924, determined by himself 

 on 19th and 20th June) does not take account of the fact 

 that the line is a close double. 



Dr. Huggins, after some failures, observed the D 3 line 

 to be double on 10th July [Ast. Nack., 3302); he also 

 notes that the less refrangible component was the fainter, 

 and that the distance apart of the lines was about the same 

 as that of the lines in the gas from cleveite, according to 

 Runge and Paschen. 



It may be added, that in addition to appearing in the 

 chromosphere, the D 3 line has been observed as a bright 

 line in nebulae by Dr. Copeland, Professor Keeler and 



