DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 437 



produced in 92246 + x by a decrease of Aj = 72820 in its denominator. The result 

 is that 



P ( oo ) = S (1) = 92266 = N/{1-090264} 3 



u = 11191-8 

 v = 13680-0 

 S^l) = -41864'S 



The set of S (l) lines would then be 



-41864-3, -36493-6 or 897,* -33844'!. 



On the two latter u, eu, ev links as sounders should give the following lines, 

 below which are placed the nearest observed, 



25301-8 or 297'3 22652'3 



(2) 25299-1 7 (W.) (4) 22G366 (C.R.) 



, 24007'! or 3'2 21357'6 



' (20) 23993-82 (R.) 4'45 (W.) (10) 21357'43 (R.) G'57 (W.) 



I 26495-3 23846 



| ... (2) 23841-9 (W.) 



They are not satisfactory sounded lines, but are given as material at disposal only, 

 M.S.J and e.S 3 .u are really good. 



There is a striking triplet which has all the aspect of being a S (l) set except that 

 of position. It is 



(2) 186117 (W.) 2648-9 (5) 21260'21 (W.) 



(0) ... 09-94 (R.) 2652-3 (3) 21262'25 (R.) 5371-3 (10) 26633'64 (R.) 



Its separations give support to the values obtained above. It is a parallel set to 

 our adopted S (l), separated from it by 152307. I have not been able to recognise any 

 arrangement of links which give this value although 2b + a, and ev + b are close 

 to it.t 



* Sounded from observed line. 



t There is the possibility to be kept in mind that it may be a real and independent S set of lines, not 

 analogous to the set considered in the previous elements. If so, it must have the same limit and 

 s(l) = 77036-64 = N/{1-193177} 2 . Now the s sequence depends on the atomic volume, although the 

 exact relation is not known. In the next group, the alkalies, the denominator is of the form 987 + kv, 

 where v is a number proportional to the atomic volume. If here the group constant be '99, the 

 denominators of the two types of s sequences can be expressed as -99 + kv and -99 + 2fa;. In other 

 words, this new type may depend on twice the atomic volume. 



