418 DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



satellite. But EDER and VALENTA observe 7 7 59 '5 and not 7757, whereas the former 

 if a satellite should be fainter than the latter. The question is discussed in [I.] and 

 also in the present communication, and the weight of evidence would appear to be 

 against the existence of satellites in Rubidium. I have entered the third line as 

 6298 '8 instead of K.R.'s value of 62987, because the former value agrees with 

 independent observations by E.V., S., and E.H., and gives a better value for v. 



Cs. The first were observed and allocated by PASCHEN, the second first by 

 LEHMANN, but the measures are those of PASCHEN. SAUNDERS was the first to draw 

 attention to the satellites. 



The last line, 5118, was observed by HARTLEY, and is clearly the D 2 (12) line. The 

 corresponding D! (12) would be in the neighbourhood of 5256'96, or D 2 (9). 



Mg, Ca. The lines were all assigned by RYDBERG. He also wrongly assigned two 

 lines about 12000 to MgD(l). The measures are by K.R., except the ultra-red in 

 Ca due to PASCHEN (' Ann. d. Phys.,' 29, p. 655). 



Sr. Assigned and observed by K.R., except ultra-red due to PASCHEN. 



Ba. Assigned by SAUNDERS (' Astrophys. Journ.,' 28, p. 223). The measures are 

 those of K.R., except those with S. attached. 



Zn. The lines down to D 2 (6) with the exception of the satellites were assigned by 

 RYDBERG. The measures, as well as allocations of the others are by K.R. 



Cd. Lines to D 2 (4), satellites excepted, assigned by RYDBERG. The remainder 

 allocated and all the measures by K.R. 



Eu. The Eu spectrum gives evidence of much collateral disturbance, and the 

 unobserved D lines are possibly displaced in this way. 



Hg. The D n lines to D n (4) assigned by RYDBERG, to D 3 (5) satellite by K.R. 

 D! (6) to Dj (16) by MILNER (' Phil. Mag.,' (6), 20, p. 636). 



Al. RYDBERG gives the first two doublets without the satellites and assigns 11280 

 wrongly to D (l). Further he assigns D lines to the S series, but the observations at 

 his disposal were too inexact. The measures and allocations are by K.R. 



In. RYDBERG down to Di(5) with satellites of first two. The remainder and all 

 the measures by K.R. As in the S series it should be noted how the D 2 lines are 

 more persistent than the Dj. 



Tl. RYDBERG gives all except from D^IO), and he gives D 2 down to m = 15. 

 The measures given are by K.R. except those below 2105, which are due to CORNU. 



The F Lines. 



BERGMANN in 1908 (' Z. S. f. Wiss. Phot.,' 6, see also ' BEIBL.,' xxxii., p. 956) 

 measured lines in the ultra-red spectra of the Alkalies and observed in Cs a number of 

 doublets which clearly formed a series, and a few lines in Na, K, Rb which were 

 evidently analogous. It was, however, RUNGE ('Astrophys. Journ.,' 27, p. 158; 

 ' Phys. Z. S./ 9, p. 1) who pointed out the dependence of the limit of the series on 



