Sir Norman Lockyer, On the Order of Appearance of 



" On the Order of Appearance of Chemical Substances at different 

 Stellar Temperatures." By Sir NORMAN LOCKYER, K.C.B., 

 F.B.S. Keceived February 17, Eead February 23, 1899. 



In a paper on the " Chemistry of the Hottest Stars,""* in 1897, I 

 stated the results so far arrived at concerning the order in which cer- 

 tain spectral lines appeared and others disappeared in stars arranged in 

 a series of ascending temperatures. Since that paper was written 

 many important advances have been made, so that I have been able 

 in the meantime to considerably extend the research. Among these 

 advances I may mention the following : 



1. With regard to the metals, my recent note on the enhanced lines 

 in the spectrum of a Cygnif enables us to deal with the lines observed 

 at the highest temperature in the spectra of the following substances, 

 Fe, Mg, Ca, Sr, V, Ti, Ni, Mn, Cr, and Cu. 



The temperature ranges of the enhanced lines of these metals have 

 been investigated with the following results : 



I pointed out in the note referred to that the enhanced lines of the 

 above substances seemed to account for almost all of the more marked 

 lines in a Cygni. It is on this ground that I have investigated their 

 behaviour in other stars before waiting for the results of the complete 

 inquiry. Another reason has been that although in addition to the 

 enhanced lines of the metals shown in the foregoing table, those of 



Ba, Cd, Mo, La, Sb, Pd, Ta, Eh, Er and Yt, Ce, Wo, U, Zr, Pb, Co, Bi, 



have already been investigated with lower dispersion, and a spark ob- 

 tained with the use of a much less jar capacity, so far I have no 



* Roy. Soc. Proc.,' vol. 61, p. 148. 

 f Supra, p. 320. 



