420 
DR. W. M. HICKS; A CRITICAL STUDY OF SPECTRAL SERIES. 
Taking this as F { oo) and using the f{m) sequences as given by the formula (p. 412) 
it is possible to calculate the positions of the lines in question. The results are given 
down to = 8. 
m. 
F. 
35012-30. 
F. 
Calculated. 
Observed. 
Observed. 
Calculated. 
2 
22652-26 
...(3) 52-88 
11-98 
(...71-08) 
47372-34 
3 
28092-94 
(...93-54) 
11-85 
(...30-16) 
41931-66 
4 
30594-43 
...(1) 95-63 
13-50 
(...31-36) 
39430-17 
5 
31948-38 
(...47-00) 
12-02 
(...77-05) 
38076-22 
6 
32763-63 
...(1) 62-39 
12-76 
...(iTi) 63-13 
37260-97 
7 
32292-00 
(...92-05) 
12-14 
(.. 32-23) 
36732-00 
8 
33653-80 
...(3) 53-04 
36370-80 
\_Note .—Si displacement on F ( oo) gives a change 6'045.] 
2. F requires sounding. (2) 35923• SQ.c.?; = 4737DOS. 
3. (-5Si) (3) 28063-32 = ...93-54; F requires sounding. (Sj) (1) 37508-25.?; = 41930-21. 
4. (-2Si) (2) 39419-27 = ...31-36. 
5. (-28i) (2'ft) 31934-91 = ...47-00; (2Si) (1) 38089-14 = ...77-05. 
6. For F. (4/1) 37263-13; also (-6Si) (< 1) 37226-34 = ...62-88, or the same. 
7. ?/.(!) 37720-05 = ...92-05; also (-3Si) (4) 33274-11 = ...92-24; (2) 32304-23.?; = 36732-23. 
The mean limit is 35012'37. The set form an additional test that the extrapolated 
lines 16013 really exist. It is curious to note that the even orders of F only show 
directly observed lines, whilst the odd show displaced limit lines. The F lines are far 
to the violet end and come into the observed region only when weakened by high 
order. The F lines are all linked to lines of higher frequency by the 1864 link, also for 
7n = 4, 6 to lines of lower frequency. The same tendency is shown in F to lower 
frequency, any such to higher frequency lead to unobserved regions. This fact is 
important as showing that at least here the 1864 separation enters in the link 
relation, and not as a direct displacement on the limit. 
To the F 3 (oo) limit corresponds a 1864 triplet series parallel to that originally 
considered. I have been able to follow it up in the same way as the foregoing as far 
as m = 26 at least. It accentuates the evidence for the displaced sets but as that is 
sufficiently supported by the results already discussed it would seem unnecessary to 
overburden the present communication with additional detail. Whenever the actual 
relations of the various displaced lines to one another are the subject of discussion 
these details will be of the first importance. A knowledge of these relations shonld 
be expected to throw a flood of light on the constitution of spectra, but this new 
question cannot be taken up here. It may be noted, however, that the first F and F 
lines of the triplets up to 7ti =10 are given in the table under F 3 . 
