PROF. A. FOWLER ON SERIES LINES IN SPARK SPECTRA. 
241 
with the fact that the more refrangible component of the “ 4481 ” lines is also the 
stronger. 
While it is thus probable that the “ 4481 ” series is numerically related to the D 
series of Wide doublets, there are objections to regarding it as directly derived from 
that series— 
(l) The “ 4481 ” lines, unlike the doublets, do not occur in the ordinary arc ; 
(2) The separation of the components of the “ 4481 ’ lines is much too small compared 
with the F doublets of Ca, Sr, and Ba ; the latter are roughly proportional to the 
squares of the atomic weights—Ca 65, Sr 285, Ba 575—-and a corresponding F series 
of Mg would be expected to have a separation of about 20 in place of the 0’99 actually 
observed in the “ 4481 ” lines. 
The probable nature of the relation, however, has been revealed by the discovery 
of a new system of doublets, with which the “ 4481 series appears to be directly 
associated. Before referring to these new lines it will be convenient to give further 
data for the Wide doublets, for comparison with similar data which will appear 
later for the new series. On the assumption that the variable part of the 
expression for the first observed pair of the D series is identical with one limit of the 
o 
“ 4481 ’’series, the corrected limit of the less refrangible components (I.A.) becomes 
49,779-0 + 35,729-6, or 49,778‘0 + 35,730'6* = 85,508-6, and that of the more refrangible 
components, 85,508"6 + 9P5 = 85,600"1. These values have been utilised in the 
construction of Table YI. It is only necessary to explain that the symbols mD, mS, 
Table YI. — Mg Wide Doublets. Revised Data. 
Limits 
785,508-6. 
I 85,600-1. 
TO. 
D series. 
S series. 
X(I.A.). 
n. 
Sn. 
toD. . 
A (I.A.). 
n. 
8n. 
toS. 
1 
- 2795-5231 
-35,761-15 
91-54 
121,269-7 
-2802-6981 
-35,669-61 
121,269-7 
2 
2797-989 
35,729-63 
(35,730-6)1 
92-44 
49,779-0 
49,778-0 
2936-496 
34,044-44 
91-48 
51,464-2 
2790-768 
35,822-07 
49,778-0 
2928-625 
34,135-92 
51,464-2 
3 
57,546 
27,962-6 
57,027 
28,481-6 
57,639 
27,961-1 
57,115 
28,485-1 
* Assumed wave-number of satellite to A 2797'989. 
t First P doublet. 
J Wave-number of probable satellite. 
2 I 
VOL. CCXIV.-A. 
