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



It was shown in [I.] that the F series of the alkalies could be represented by a series 

 of the form m+l a(l 1/m). The same is the case with the Al and Zn groups. 

 As a is so small and varies so little it can scarcely be a function of the atomic weight. 

 The atomic volumes of the elements are much more even and it may be a function of 

 them as is the case with the p-sequence. In fact, in the case of the alkalies, the a 

 are not far from being proportional to v, 2v, 2v, 3v, for the four elements considered, 

 but the data are so inexact and uncertain that it seems not worth while to undertake 

 an exhaustive numerical discussion. 



We do not know that the chief lines of these sets are those depending on m = 3. 

 If lines exist depending on m = 2 they would all be in extremest reel, in fact with 

 wave-lengths comparable with those of electro-magnetic waves capable of being 

 experimentally excited, and it is possible that VF(2) might be the same for all low 

 melting-point elements and as for He (see [I.]). For m = 1 we should expect the 

 lines of negative wave number in regions which have been observed and in which no 

 such lines have been seen. 



The F series in the high melting-point elements, on the contrary, are profoundly 

 influenced by the atomic weight term. Either the lines observed belong to a different 

 type from those of the others, or they are based on a normal type of aggregation 

 which is modified by collateral and other types of displacement due to the splitting 

 up of the typical aggregations, or to a more complex system of new aggregations. 



The notation F for these series was adopted in [I.] under the idea that the 

 sequence for it was of a more fundamental nature than the others, and that 

 impression is rather strengthened by the present discussion. It has been seen, for 

 instance, how the limits of PASCHEN'S singlet S' series in the Zn group depend on it. 

 It would be interesting to know whether similar series appear in the alkalies and 

 aluminium group. 



The Value of the Chin. 



The further knowledge now gained as to ways in which the oun or the A enters 

 in the constitution of spectra, enables a much closer approximation to its actual value 

 to be obtained than was possible from the consideration of the doublet and triplet 

 separations themselves. Amongst the principal aids are (l) the separations themselves, 

 (2) the dependence of the first D denominator on a multiple of A, (3) in the triplet 

 elements, on the collateral relations between associated lines, (4) the satellite 

 separations in the D series, (5) the order separations in the D series which show 

 no satellites, (6) collaterals depending on A. Of these, Nos. (l) and (4) have the 

 great advantage that the values depend only slightly on the exactness of the limit 

 (the value of ), but (4) has the disadvantage that only small multiples of S are 

 involved, and (l) only A itself. There are also various uncertainties which show 

 themselves when a high order of accuracy is desired chiefly in the elements of the 

 3rd group. No. (2) has the great advantage of giving considerable multiples of A, 



