336 DE. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



Radium emanation 424 



analogue of 1864 in XF 426 



,, general considerations for S.D 433 



value of S ( oo ) and e link 436 



,, P( oo ) and w.v links 437 



S series 438 



D series 440 



,, source of 5648 separations 441 



value of the oun , 442 



Argon, D series 443 



( - 58) D series 444 



F and P series 445 



value of the oun 447 



Analogue of 1864 XF . . 449 



Neon 449 



F series 451 



,, parallel F sets 452 



F series 453 



D 454 



S 456 



,, e link 456 



,, normal D and S lines 458 



,, value of the oun 461 



WATSON'S separations 463 



Rossi's series 466 



Table of constants . . . 468 



THE present communication has two objects. Its subject matter is an attempt to 

 obtain some knowledge of the series relations in the spectra of the group of the 

 monatomic rare gases Ne to RaEm, whilst the methods employed will serve to 

 illustrate the fundamental importance as instruments for further research of the new 

 facts brought to light in the previous communications.* The importance of the first 

 object will be generally acknowledged, but it does not yet seem to be realised how 

 definite and exact those new relationships are, even in their as yet undeveloped form, 

 and how powerful an instrument is placed in our hands for the analysis of spectra. 

 It may be well therefore to commence by a brief resume of some of these laws as 

 applied in the succeeding pages. Further, as the establishment of the results 

 obtained must by its nature depend on the numerical comparison of a very large 

 number of lines in all five spectra, and as this evidence must be fully set out to 



* " A Critical Study of Spectral Series," Part I, ' Phil. Trans.,' A, vol. 210, p. 57. 



Part II. 212, p. 33. 



Part III. 213, p. 323. 



Part IV. 217, p. 361. 



These will be referred to respectively as [I.], [II.], [III.], [TV.]. 



