On the Chemistry of the Hottest Stars. 



191 



It seemed perfectly clear then that in the sun " we were not dealing 

 with iron itself, but with primitive forms of matter contained in 

 iron, which are capable of withstanding the high temperature of the 

 sun, after the iron observed as such, has been broken up, as 

 suggested by Brodie."* 



On this view, the high temperature iron lines of the chromosphere 

 represent the vibrations of one set of molecules ; while the lines 

 which are widened in spots correspond to other molecular vibrations. 

 Similarly, the idea of different molecular groupings provides a 

 satisfactory explanation of the varying rates of movement of iron 

 vapour indicated by adjacent lines, the lines being produced by 

 absorption at different levels and at different temperatures. 



§ 2. How the Hypothesis has fared. 

 The Main Points. 



Only some of the views have received general acceptance, those 

 referring to the breaking up of the solid metal giving a continuous 

 spectrum into smaller molecular groupings giving fluted and line 

 spectra. 



My view as to the subsequent dissociation of molecules, when once 

 the line spectrum stage has been reached, is still rejected by many. 

 For myself, 1 am not surprised at this. In a question of such tran- 

 scendent importance, caution must be redoubled ; an absence of work 

 and expression of opinion in such a line of inquiry with questions of 

 pure science only involved, is almost inherent to the nature of the 

 investigations. 



The chemist has little interest in an appeal to celestial phenomena, 

 and astronomers do not generally concern themselves with chemistry, 

 The region investigated by the chemist is a low temperature region 

 dominated by monatomic and polyatomic molecules. The region I 

 have chiefly investigated is a high temperature region, in which 

 mercury gives us the same phenomena as manganese. In cases 

 where the two regions overlap, vapour density determinations and 

 other work have been in harmony with the spectroscopic results, e.g., 

 the changed density of iodine at changed temperatures. 



Another, but less direct, argument in favour of dissociation, inde- 

 pendently of the changes in the intensities of the lines, was based 

 upon some observations I had made in an attempt to work out a 

 spectroscopic method for the detection of impurities. I noted the 

 presence of what I termed "basic lines," that is, short lines which 

 remained common to two or more spectra, after " long lines " had 

 been eliminated as being due to impurities. 



I now refer to these different points seriatim. 



* ' Eoy. Soc. Proc, vol. 32, p. 204. 



