High' Frequency Spectra of the Elements. 713 



suggests that the L system is- situated the further from the 

 nucleus. 



It was shown in Part I. * that the linear relation between 

 v* and N — b was most naturally explained i£ the vibrating 

 system was a ring of electrons rotating round the central 

 nucleus with an angular momentum which was the same for 

 the different elements. This view has been analysed and put 

 in a more generalised form in a letter to ' Nature 'f, written 

 in answer to criticisms made by Lindemann J. 



Summary, 



1. Every element from aluminium to gold is characterized 



by an integer N which determines its X-ray spectrum. 

 Every detail in the spectrum of an element can there- 

 fore be predicted from the spectra of its neighbours. 



2. This integer X, the atomic number of the element, is 



identified with the number of positive units of 

 electricity contained in the atomic nucleus. 



3. The atomic numbers for all elements from Al to An 



have been tabulated on the assumption that N for Al 

 is 13. 



4. The order of the atomic numbers is the same as that of 



the atomic weights, except where the latter disagrees 

 with the order of the chemical properties. 



5. Known elements correspond with all the numbers be- 



between 13 and 79 except three. There are here 

 three possible elements still undiscovered. 



6. The frequency of any line in the X-ray spectrum is 



approximately proportional to A(X — 6) 2 , where A 

 and b are constants. 



I wish to thank Prof. J. S. Townsend, F.P.S., for providing 

 me with every facility for carrying on this work, which has 

 been greatly assisted by a grant from the Institut Inter- 

 national de Physique Solvay. 



Electrical Laboratory, 

 Oxford. 



* Loc. cit. p. 1032. 



t Moseley, ' Nature/ Jan. 15 (1914). 



X F. A. Lindemann, ' Nature,' Jan. 1, Feb. 5, 1914. 



