Further Observations of Enhanced Lines. 



443 



Name of Star. 



Calcium group. 



Iron group. 



Bellatrix 

 I Tauri 

 Eigel 

 rj Leonis 

 a Cygni 

 7 Cygni 



C* Idull 



o Orion is 



Ca 

 Sr 



[Enhanced lines of barium 

 probably do not ap- 

 pear] 



Fe, Mn. 



Co, m. 



iron and manganese show their enhanced lines at temperatures as high 

 as £ Tauri, while cobalt and nickel do not extend higher than Rigel. 

 Among the substances recently examined, the case of silicium is of 

 special interest. The enhanced lines of this substance, two of which 

 have wave-lengths about 4128*6 and 4131 "4, are amongst the most 

 conspicuous lines in a Cygni and remain distinctly visible even in 

 Bellatrix, after the lines of iron, manganese, nickel, and cobalt have 

 vanished. In its stellar behaviour then, this substance resembles Ca 

 and Mg. 



So far as the work has gone, the comparison of the enhanced lines 

 with the spectrum of the chromosphere reveals several facts of im- 

 portance. In the case of iron, I have already pointed out* that the 

 enhanced lines were all present in the chromosphere during the 

 eclipse of 1896, and most of them in that of 1893, their intensities 

 being greater than those of the corresponding Fraunhofer lines. 

 Many of the characteristic arc lines of iron also appear in the 

 chromosphere, but the presence of the enhanced lines with such 

 great intensities indicates that at least in some parts of the chromo- 

 sphere the temperature of the iron vapour is considerably higher 

 than that of the iron vapour which is most effective in producing the 

 Fraunhofer lines. A similar result is obtained when other sub- 

 stances are considered. The special importance of the enhanced lines 

 in the chromosphere is shown by the following figures relating to 

 substances which have been most completely studied : — 



No. of enhanced lines of Fe, Mg, Ca, Mn, Ni, Co, Ti, so far 



tabulated in the region F to K 63 



No. of these lines photographed in eclipse of 1893 28 



Percentage of enhanced lines of Fe, &c, in eclipse lines of 



1893 44 



No. of enhanced lines photographed in eclipse of 1896 .... 41 



Percentage of enhanced lines of Fe, &c, in eclipse of 1896. . 65 



* ' Roy. Soc. Proc.,' vol. 60. p. 475. 



