SIR WILLIAM CROOKES ON SCANDIUM. 45 



next in order to boron ") would ultimately form boron by a quadruple sub-division. 

 The comparatively small quantities of ytterbium and scandium in these minerals may 

 easily be accounted for by the assumption that they are more unstable forms of 

 matter than yttrium and boron. 



The fact that these bodies give totally distinct line spectra has not the significance 

 it formerly was supposed to have, for now we know of different line spectra given bv 

 the same body. Argon, with its red and blue spectra, is a case in point, and 

 GOLDSTEIN, as a result of his work on the spectra of Cs, lib, and K, has come to the 

 conclusion that the property of emitting two separate line spectra is a general one. 

 Moreover, between the line spectra of radium, uranium, and helium bodies which 

 are supposed to be associated genetically there is no similarity or line in common. 



