104 INORGANIC EVOLUTION. [CHAP. 



sociated in the sun. It merely shows that the apparently similar 

 portions of the two lines in the solar spectrum are produced at dif- 

 ferent elevations in the solar atmosphere. The stronger iron line 

 will be affected in a sun-spot as much as the other one, but it is 

 the portion of the line produced at the same level as the other line, 

 and may be masked completely, or very largely, by the emission line 

 produced at a higher level, while the second absorption line in the 

 solar spectrum may be entirely unaffected, being produced at a still 

 higher altitude." 



" This also explains why some of the lines (the short lines generally) 

 of an element may be most prominent in sun-spot spectra, while others 

 (generally the long lines) are those most frequently seen in promi- 

 nences or in the chromosphere." 



My thirty-three years' work at solar physics leaves me with such 

 an oppressive feeling of ignorance that I willingly concede to Mr. 

 Jewell a knowledge so much greater than my own as to give him a 

 perfect right to dismiss all my work in two lines ; but I am compelled 

 to point out that he has not carefully read what I have published. 



A comparison of the facts brought together on page 26, for instance, 

 drives his last paragraph into thin air ; it is distinctly shown that we 

 have to do with the short lines in the chromosphere and with the long 

 lines in spots, the exact opposite of his statement. Mr. Jewell does not 

 run counter to my views in supposing that different phenomena are pro- 

 duced at different elevations. I thought I had abundantly proved in my 

 eclipse observation of 1882 (Chemistry of the Sun, p. 363), and the later 

 evidence will be found on p. 41, et seq., that the iron lines, to take a 

 concrete instance, are produced at different heights in the solar 

 atmosphere ; and that was one among many reasons which compelled 

 me to abandon the thin reversing layer suggested by Dr. Frankland 

 and myself in 1869 in opposition to KirchhofFs view. But surely the 

 more we consider the solar atmosphere as let out in flats, with certain 

 families of iron lines free to dwell in each and to flit a discretion, the 

 more a dissociation hypothesis is wanted. And beyond all this, we 

 have to take into account that at the sun-spot maximum no iron lines 

 at all are seen amongst the most widened lines, while at the minimum 

 we have little else. 



The real bearing of the new work on the dissociation hypothesis 

 has been accurately caught by Professor Hale, as I shall show later. 



Another very interesting part of Mr. Jewell's work refers to the 



phenomena of absorption. There is room for plenty of work here. 



As I pointed out in 1879, we get unequal widenings, " trumpetings," 



and a \vhole host of unexplained phenomena.* It is clear that the 



* Chemistry of the Sun, pp. 380387. 



