PEOF. A. FOWLER ON SERIES LINES IN SPARK SPECTRA. 
249 
The first striking result derived from these calculations is that the separation of the 
second member is 30'5, which is exactly that of the cl and s doublets of the “ F.P.” 
system. Hence it is suggested that the variable parts mP l5 mP 2 are really identical 
with corresponding terms of the p series (Table VIII.). The differences are in fact 
not too great to be attributed to defects of the simple formulae employed. Thus the 
P and p series may also be considered as running parallel to each other at a distance 
apart of Pco— pco = 121,2697 — 51,464'2 = 69,805'5 = S(2)—S(l). Since the data 
for the p series depend upon more complete observational material than those for P, 
the latter may be corrected by the former, with the following results:— 
Table X.—Corrected Principal Series of Wide Doublets. 
Limit = 121,2697. 
m. 
A 
(I.A.). 
n. 
mP 2 . 
mPi. 
8n. 
Remarks. 
1 
2802-698 
35,669" 6 
85,600-1 
91-5 
Observed lines (Table VI.). 
2795-523 
35,761-1 
85,508-6 
2 
1240-37 
80,620-8 
40,648-9 
30-5 
1239-90 
80,651-3 
40,618-4 
- Calculated. 
3 
1026•11 
97,455-5 
23,814-2 
14-0 
1025-96 
97,469-5 
23,800-2 
Even the second pair is beyond the region photographed by Lyman in the case of 
magnesium, but it is not outside the limit of possible observation. 
The foregoing considerations leave no doubt that while the limits and separations of 
the D and S series of Wide doublets are derived in the usual manner from the first 
doublet of the P series, those of the d and 5 series of the narrower “ F.P.” doublets 
are derived from the second P pair (Wide doublets). Paschen’s work on Combination 
series appears to justify the belief that the Rydberg-Schuster law of limits, and 
Rltnge’s law as to the derivation of the limit of the Fundamental series from the first 
line of the Diffuse series, are both exact, and the parallelism of the two systems thus 
permits the accurate calculation of data for both, since data lacking in one may be 
adopted from the other. For example, the term 2s of the “ F.P.” group is given by 
calculation as 51,328'2, and Is as 119,449'3 ; both may be obtained with a much 
higher degree of precision by adopting the values 2S and IS of the Wide doublet 
system (Table VI.), which are themselves independent of formulae except as regards 
the determination of the limits of the “ 4481 ” series. The following table (XI.) may 
2 K 
YOL. CCXIY.—A. 
