xxvii.] THE CERIUM SPECTRUM. 401 



prepared in Bunsen's laboratory) between G and K is greater 

 than the number of Fraunhofer lines in that region. 



On this point I cannot refrain from quoting the following 

 remarks by Mr. Liveing : 



" The spectrum of iron .... presents thousands of lines dis- 

 tributed irregularly through the whole length not only of the visible 

 but of the ultra-violet regions. Make what allowance you please 

 for unknown harmonic relations, and for lines which are not re- 

 versible and may not be directly due to vibrations of molecules, we 

 still have a number of vibrations so immense that we can hardly 

 conceive any single molecule to be capable of all of them, and are 

 almost driven to ascribe them to a mixture of differing molecules, 

 though we have as yet no independent evidence of this." 



On this extract I need only remark that if the elementary 

 bodies are incapable of separation into their constituents by 

 ordinary chemical processes, and yet are decomposable, the 

 spectroscopic phenomena treated of in this book are precisely 

 those we should expect supposing that high temperatures do 

 really dissociate. This evidence is not to be neglected because 

 the chemist is slack in producing " independent" evidence. Mr. 

 Crookes' recent work suggests that the time is not far distant 

 when such " independent " evidence will be before the court. 



1 British Association Report, 1882, p. 483. 



D 15 



