VI.] 



CHEMISTRY OF THE STARS. 



57 



general statement, and I next pass from the general to the particular, 

 and give the detailed results recently obtained in the case of stars as 

 hot or hotter than Arcturus taking -Arcturus to represent the solar 

 temperature in the light of the most recent work, some of which has 

 already been referred to in the preceding chapters. 



Proto-metals. 



With regard to the metals, the recent work on the enhanced lines 

 in the spectrum of metals, a Cygni* and the sun's chromosphere enables 

 us to deal with the lines observed at the highest temperature in the 

 spectra of the following substances : magnesium, calcium, iron, man- 

 ganese, nickel, chromium, titanium, copper, vanadium, strontium, sili- 



cmm. 



The untouched reproductions of photographs of the spectra of the 

 chromosphere and a Cygni, given on page 53, have already shown the 

 wonderful similarity which exists between these three spectra. 



As we have to deal both with the arc and spark lines of these sub- 

 stances, for the sake of clearness I call the latter " proto-metallic " lines, 

 and consider the substances which produce them, obtained at the 

 highest available laboratory temperatures, " proto-metals," that is, a 

 finer form of the metal than that which produces the arc lines, corre- 

 sponding to the " meta-elements " imagined by Crookes. 



The temperature ranges of the enhanced lines of these metals have 

 been investigated in various stars with the following results : 



* Nature, vol. Ixix, p. 342. 



f This is one of the most extraordinary spectra which has been met with in the 

 Kensington series of photographs, as I have already pointed (Proc. Roy. Soc., vol. 

 Ixi, p. 184). While the lines of hydrogen are fairly sharp and not very broad, 

 many of the lines, especially those of the cleveite gases, are broadened almost into 



