368 



NATURE 



[August 19, 1897 



similar result is obtained when other substances are con- 

 sidered. 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. 



These numbers show that the chromospheric spectrum 

 is largely composed of enhanced metallic lines in addition 

 to the lines of hydrogen and helium. 



In the Fraunhofer spectrum enhanced lines may be 

 regarded as wanting, for in the case of iron and mag- 

 nesium, at least, they only appear with 

 the feeble intensities which they have 

 in the arc spectrum, while the charac- 

 teristic arc lines are strong. Here, 

 then, we find the cause of the dissim- 

 ilarity of the chromospheric and Fraun- 

 hofer spectrum, which is indicated by 

 the following figures : — 



i" IG. 16. — The enhanced Unes of iron and their appearance in stellar spectr, 



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

 far tabulated in the region F to K 63 



No. of these lines photographed in eclipse of 1893 in 

 the same region 28 



No. of Fraunhofer lines tabu- 

 lated by Rowland in the 

 region F to K 5694 



No. of lines photographed in 

 the same region, eclipse 

 1893 164 



Percentage of Fraunhofer lines 3 



No. of lines photographed in 



the same region, eclipse 1896 464 



Percentage of Fraunhofer lines 8 



Clearly, then, the chromosphere as 

 photographed in the eclipses of 1893 

 and 1896, is a region of high tem- 

 perature, in which there is a corre- 

 sponding simplification of spectrum as 

 compared with the cooler region in 

 which the Fraunhofer absorption is 

 produced. The spectrum of the chromo- 

 sphere is to that of the sun generally 

 as is the spectrum of a Cygni to that of Arcturus. 

 It is obvious that if we can succeed in 1898 to 

 get similar records with double the dispersion^ an 

 immense stride will have been made, and hence the 



Fig. 17. — Spectrum ol chromosphere obtained during the total eclipse of 1896, showing lines photographed between K and 



Fig. 18. — Spectrum of chromosphere obtained during the total eclipse of 1S96, showing lines photographed between G and /'. 



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



1893 44 



No. of enhanced lines photographed in eclipse of 1896 41 

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

 1896 65 



NO. 1451, VOL. 56] 



programme for the coming eclipse to which I have 

 drawn attention. 



Norman Lockyer. 



{To be continued.) 



