III. A Critical Study of Spectral Series. Part I. The Alkalies H and He. 



By W. M. HICKS, Sc.D., F.R.S. 



Received -October 25, Read December 9, 1909. 

 NOTATION AND ABBREVIATIONS. 



n = 10 8 /A. = wave-number = number of waves per cm. 



Adopted formula, n = A - N /( m + u+\- 



I \ m ! 



A is the " limit " = n when m = GO. 

 RYDBERG'S notation for the series is adopted. Thus 

 P denotes a principal series. 

 NaP the two principal series of Na. 



is the first principal series of Na. 

 (2) is the second line in, &c. 

 is (4) denotes the satellite to the fourth line in the first diffuse series of Cs. 



is referred to as D except when there may be an ambiguity with diffuse, when den. is used. 



N 



is written V (i.e., variable part of series). Thus 



VP (1) stands for the value of N/D 2 in P (1). 



F is the symbol for the new scries (fundamental) as P.S.D. stand for those already known. 

 f by itself stands for a fraction. 

 In referring to observers 



K.E. stands for KAYSER & EUXGE. 

 L. & D. LIVEING & DEWAR. 



B. BERGMANN. 



K.H. KONEN & HAGENBACII. 



L. LEHMANN. 



LE. LENARD. 



P. PASCHEN. 



E. EAMAGE. 



S. ,, SAUNDERS. 



W. WOOD. 



THE following investigation was commenced some years ago, at a time when the 

 discussion as to the atomic weight of Radium raised the question as to the dependence 

 on their atomic weights of the wave-lengths of corresponding spectral lines of 

 different elements of the same group. The arguments were necessarily vague and 

 VOL. ccx. A 461. I 9.2.10 



