PROF. A. FOWLER ON SERIES LINES IN SPARK SPECTRA. 
247 
Table YIII.—Principal Series of “ F.P.” Doublets. 
Limit = 51,464'2. 
m. 
A. 
(I.A.). 
n. 
mp 2 . 
mp i. 
Sn. 
Remarks. 
2 
9243-7 
10,815-3 
40,648-9 
30-5 
Calculated. 
9217-7 
10,845-8 
40,618-4 
3 
3615-64 
27,650-0 
23,814-2 
14-0 
Observed. 
3613-80 
27,664-0 
23,800-2 
4 
2790-84 
35,819-9 
15,644-3 
7-6 
-w 
2790-35 
35,827-5 
15,636-7 
- Calculated. 
5 
2474-37 
40,402-4 
11,061-8 
4-5 
2474-09 
40,406-9 
11,057-3 
The Principal series thus appears to be satisfactorily identified, but it is somewhat 
remarkable that it does not occur with greater intensity. 
§ 9. Relation between the Two Systems of Doublets. 
The connection of 4481 with the Wide doublets appears to arise from the fact that 
the two sets of doublets are themselves closely related. An indication of this has 
already been noted in connection with the limit of the p series. Further evidence is 
afforded by a comparison of other terms of the two systems. Thus, for the Wide 
doublets, including the case just mentioned, we have from Table VI., 
SjO0 = 85,508-6, 
S 2 oo = 85,600-1, 
2D = 49,778-0, 2S = 51,464’2, 
3D = 27,961-8, 3S = 28,483-3, 
all of which are derived from actual observations, and are, therefore, unaffected by 
any imperfections of formulae except as regards the limits of the “ 4481 ” series. The 
equations for the d, s, and p series of “ F.P.” doublets (pp. 244 and 246) give 
corresponding terms, 
