DE. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 449 



The separation 150 has been referred to as probably the analogue of the 1864 F 

 separation in X. The reasons for this supposition are based on its magnitude and its 

 occurrency curve. This separation in Kr, X and RaEm has been explicable as due to 

 a displacement close to 5A 2 on the mantissa of a d (l) sequent. In the present case 

 the example taken is not the most important F series, but its limit will be near that 

 to which the separation is due. The displacement required in it to produce a 

 separation 150 is very close to 5A 2 , in fact 5A 2 produces 149. The separation in 

 question then is caused by displacement of the normal A 2 -multiple for this series. 

 The second reason is based on the form of the occurrency curve, which shows the 

 same sharply defined single peaked curve as in X. It is represented in Plate 2, 

 fig. 5. 



It may be interesting to note that all STARR'S A + + + lines, i.e., whose sources have 

 lost three electrons, all show e links except one. They are 



(3) 23674 719-23 (3) 24393 

 (3) 23696 



(2) 24053 719-22 (4) 24772 

 721-90 (1) 23639 719-46 (7) 24359 



?F, (5). (5)24521 719-81 (3)25241 720-24. 



Neon. The principal sources* for measurements in the spectrum of Neon are 

 observations by LIVEING and DEWAR, BALY, and WATSON. These have been 

 supplemented by interferential measures by PRIEST, MEGGERS, and MEISSNER. Rossi 

 has added a few lines down to 2352. Through the kindness of Mr. W. F. MEGGERS 

 I have also had the advantage of using an as yet unpublished list of very accurately 

 measured lines made by himself and Messrs. BURNS and MERRIL at the Bureau of 

 Standards in Washington, t The lines by LIVEING and DEWAR are only roughly 

 measured, but as in the case of the other rare gases comprise many not observed by 

 others. BALY'S list extends from 6717 to 3037, WATSON'S from 7245 to 2736 and 

 contains a considerably larger number of lines. Both in BALY'S and WATSON'S lists 

 considerable gaps appear with only a few strong lines, especially between 4250 and 

 3500. These are filled by a number of weak lines observed by LIVEING and DEWAR. 

 These latter are very important for the complete discussion of the Ne spectrum as 

 they represent the scattered displacements and linked lines of low order series lines 

 which normally should occur as single strong lines but which are here wanting. 



* LIVEING and DEWAR, 'Roy. Soc. Proc.,' vol. 67, p. 467 (1900); E. C. C. BALY, 'Phil. Trans.,' A, 

 vol. 202, p. 183 (1903); H. E. WATSON, 'Roy. Soc. Proc.,' A, vol. 81, p. 181 (1908); J. G. PRIEST, 

 Bull. Bur. Standards' (U.S.A.),. vol. 8, p. 2 ; W. F. MEGGERS, 'Bull. Bur. Standards,' vol. 12, p. 198 

 (1915)'; K. W. MEISSNER, 'Ann. d. Phys.,' vol 51, p. 115 (1916); R. Rossi, 'Phil. Mag.,' vol. 26, p. 981, 

 (1913). 



t Referred to below as B.M.M. 



3 P 2 



