DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 
GL 
The first two X\ for S 5379T and 4711'69 are extrapolated from the observed faint 
line 4498 by taking = 2632‘5 and V 2 = 1904, which is a])Oiit the mean value of 
the i^’s. Several other alternatives might be taken, but this gives the best analogy 
with Cd and Hg. The first three lines give for the formula 
n = 40364-08-N/{m+l-291G03--047520m-'}2 
with errors for m = 4, 5 of '14 and '36, probably within any observational error. The 
values of the A come out (with v-^ = 2630‘5 and I'a = 1004) to 
Ai = -051222 = •022162-2(;^ 
As = -018327 = -007929^1;'. 
Ag is intermediate to those for Cd and Hg, viz., -008208and -007500-?^' 
respectively, but for the latter A^ are ' 0182897 ^^ and - 0219537 .t^^, so that Aj for Eu is 
a slightly larger multiple of than for Hg, supposing that the atomic weight of Eu 
is correctly given as 152-03. 
The ratio (a +W)/(/z +W), which ought by analogy to be -21520, is -21246. But 
the uncertainty of the top line might account for this: e.g., if this supposed line be 
taken 2-2 A.U. greater this ratio would he -21520 with m + W = -310572. 
There is some appearance of a satellite series for EuS., viz., tlie lines whose wave 
numbers are 
812 ( 1 ) (18516-60) 
822 ( 1 ) (21150) 
812 ( 2 ) 30090-02 
based on 22155-46, 
2633*13 32723-15. 
These give the formula 
40361-90-N/{m+l-294528-053875m-'}", 
in which the calculated values of X for m = 4 and 5 differ from the observed by 
-12, - 41 . The limit is so close to the former that they may be taken as coincident, 
indicating, therefore, that the lines are satellites as ordinarily understood. There 
appear, also, to be series associated with these. For instance, writing the wave 
numbers, with separations. 
Si. 
t'l. 
S2. 
S3. 
r (18858)* 
2633 
21491-37 (1 + ) 
998 
22489-34 
(1) 
lor (18856)* 
2630 
(21486) 
1003 
22489-34 
(1) 
30090-02 (3) 
2633*13 
32723-15 (4) 
1001*38 
33724-53 
( 1 +) spark 
34365-08 (3) 
2633*86 
36998-94 (4) 
36440-76 (2) 
37604-15 (1 + ) 
38325-24 (2) spark 
38789-61 (2) 
39128-98 (1) spark 
the numbers in brackets denoting intensities. 
[* See note at end.] 
