246 
PROF. A. FOWLER ON SERIES LINES IN SPARK SPECTRA. 
the intervals therefore suggests that one belongs to the p series while the other is a 
“combination” doublet. We have, in fact, the following numerical relations with 
the term 2d given by the limit of the more refrangible (stronger) components of the 
“ 4481 ” series 
49.779- 0-25,9787 = 23,800-3, 
49.779- 0-25,964-1 = 23,814-9. 
23,800-3 + 27,664-0 = 51,464'31 
23,814-9 + 27,650'0 = 51,464’9 j 
mean 51,464"6. 
The last number is not far from the approximate limit calculated for the p) series, 
and it is suggested that the lines at A 3615 form the p> doublet while the other pair is 
a combination derived from this and the limit of the “ 4481 ” series (/go— 3p, or 
d—3p). 
A striking confirmation of this conclusion is afforded by the fact that the term 2S 
for the Wide doublet series (Table VI.) is 51,464"2. This is not only in close 
accordance with the limit for p calculated above, but is an important indication of the 
intimate connection of the two systems of doublets. It will suffice for the present to 
note that the limit of the p series of “ F.P. ” doublets appears to be given by the 
difference between the limit of the subordinate Wide doublets and the wave- 
number of the first observed S line which has a positive value; or, symbolically, 
p go = 2S = S co — S (2). 
The agreement is too close to be regarded as accidental, and assuming the relation 
to be true, the limit of the^i series can be determined very exactly. The limit of the 
“ 4481 ” series (giving 2D and thence Sco) has been found with considerable precision 
and the wave-number of the line A 2936"496 giving S (2), has also been accurately 
determined. Hence, with very small probable error, the limit of the p series may be 
taken as 51,464*2. The limits of the d and s series (40,618"4 and 40,648"9) are 
probably also not far from the truth, and the wave-numbers of the components of the 
first p pair may therefore be deduced by the Itydberg-Schuster law. Hence, although 
only the second p doublet has been actually observed, there are sufficient data for the 
calculation of Hicks’ formulae for the series, namely, 
p 2 (m) = 51,464'2 — 
4x 109,679-3 
m + 1"305940 — 
Q‘041388 
m 
pfim) = 51,464-2- 
4 x 109,679-3 
m+ T307258 — 
Q-04155 6V 
m 
The positions of the first four doublets calculated from these equations are as 
follows:— 
