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IL A Critical Study of Spectral Series .— Part II. The p aad s Sexpuences and 
the Atomic Volume Term. 
By W. M. Hicks, Sc.D., F.R.S. 
Ecceived January 24,—Read March 7, 1912. 
Notation and Abbreviations. 
Part I. refers to the First Communication on this Subject in the 'Phil. Transj A, 
rot. 210, _p. 57 (1910). 
n = 10®/A = wave number = number of waves per cm. 
Adopted formula «, = A - N/(m + y + almp. 
A is the limit of the series = ti when ni = c&. 
vi, V 2 denote the first and second triplet separations. 
Ai, A 2 denote the differences in /x which give rise to I'l, V 2 . 
w denotes the (atomic weight)/100. 
V denotes the atomic volume. 
Rydberg’s notation for the series is adopted. Thus— 
P denotes a principal series, S sharp, D diffuse, F the series in the ultra red whose limits depend 
on the first D sequence. K. and R. call the S the 2nd associated and D the 1st associated 
series. F is often referred to as Bergmann’s series. 
ZnS denotes the three shaiqj series of Zn. 
ZnS 2 the second S series of Zn. 
ZnSi (3) the 3rd line in the first S series of Zn. 
HgDoi (3), HgD 22 (3) denote respectively the chief line and the first satellite of the 3rd order in 
the second diffuse series of mercury. 
N/(-m +/X + a/TO)2 in any series, say P, is referred to as VP (m), the V standing for variable part. 
K.R. stands for Kayser and Runge. 
E.H. stands for Exner and Haschek. 
The present communication is in continuation of one presented to the Society in 
1909. The greater part of the work was completed at that time, and it was hoped 
that it would be published shortly afterwards. Certain points, however, arose which 
the author was anxious to settle, and this led to a consideration of a number of 
specti’a in which series of the ordinary type had not yet been recognised. He hopes 
to deal with some of the most interesting points which hax'e come to light in the 
VOL. CCXII.-A 485. F Published separately, June 17, 1912. 
