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



to this new limit, with A l = 666, is 48*30. The difference between this and the 

 observed 4878 is just within our assumed possible errors on two lines. 



Again, the double line 20600'97, 02'02 apparently reproduces itself in the F group, 

 as MEISSNEK says 17081 shows also a weak component. It is also in evidence in 

 another relation as we shall see immediately. 



The existence of parallel F series with WATSON'S separations and also 1932 has 

 already been pointed out, viz., 



1932 F(l) 1429 422 



If these depend like the others on D series, the same separations should be found in 

 the reverse order. They do not appear with D 1} but they are seen with the stronger 

 line D 2 = 20600, with which also the linkage relation enters. Thus 



1428-68 (2) 20600-97 ***** 



n 

 1428-46 (8)18753 419-13 (1)19172- Tm 220SO 



1 1429-73 (0)20602-02 1428'40j (4 ' 



in which there is also a mesh between 19172 and 22030 and a link back from 18753. 

 There may also be a forward 1932 linked line if L.D. has d\ = I'l. It is striking 

 that a mesh is repeated in the F ( 1 ) set. Thus 



1429-38 18510'84 422'50 



1708F46 18933*34 



1430-24 1851T70 421-64 



The separation of the 20600 lines is practically repeated in the 18510. 



The parallel D set, with I) 2 = 20556, also shows traces of the separations, with the 

 mid lines not seen, in analogy with the weak mid one just considered. Thus 



(7) 18709 417-86 [19127] 1429'42 (3) 20556'84 



The absence of the corresponding lines connected to 20551 may be due to the 

 scattering of the lines by displacement. The wanting lines should be [19122-07], 

 [18704'6], the former corresponding to the weak 19172 of the second D group. Now 

 we find strong lines corresponding to both these at the same separations ahead and 

 suitable for the same displacements, viz., 



[19122-07] (1) 19172-29 



20-79 20-27 



(5) 19142*86 (4) 19192'56 





