157 
value of the fraction which oceurs in the formula of the 2°¢ sub- 
ordinate series. LORENTz *) too holds the same idea in his theory on 
the ZrrMAN-effect, where he says: “In connection with this, it should 
also be noticed that, in RypBerG’s formulae, every frequency is 
presented as the difference between two fundamental ones”. A more 
independent meaning is assigned to these fractions by Hicks ®), who 
gives them the name of “sequences”. 
He distinguishes viz. four kinds of them: 
1. Principal (P) sequence. 
2. Sharp (S) sequence. ' 
3. Diffuse (D) sequence. 
4, Fundamental (/’) sequence. 
In agreement with the theory given by Rrrz ®) Hicks expresses himself 
as follows *): 
“Tt appears, that, whatever the kinetic configuration may be, which 
is the source of the vibrations, the light periods depend on the differ- 
ence of frequency of two systems each with distinguishing train 
of frequences”. 
In Dunz*) we find the values of these systems calculated and 
indicated as mp, ms, md, and mAp, in which we recognize Hicks’s 
sequences, and about which we may notice that when we confine 
ourselves to one component, all the series and combinations are 
formed from these four “sequences”. 
In the following manner this system may at once be reduced to 
order, so that it is easy to survey: 
All the series and combinations may be graphically represented 
by one and the same curve, which is subjected to four different 
rotations with regard to the original system of axes. All the series 
that are represented by curves of equal rotation, belong together 
and differ only in asymptote. They may be changed into each other 
by a translation of the curve parallel to the y-axis. We shall there- 
fore call them Zranslation series. The asymptotes may be found 
from a curve with the same or with another rotation. So every 
spectral line is determined by its number on the curve and by the 
asymptote of this curve. 
Before entering into a fuller explanation by means of the annexed 
plate, I should first point out the necessity of the introduction of 
1) Theory of Electrons etc. p. 128. 
2) Phil. Trans. 210 A 1911 p. 57 et seq. 
3) Magnetische Atomfelder und Serienspektren Ann, d. Phys. 25. 1908 p. 660 et seq. 
ay ke .pe 96. 
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