DE. W. M. HICKS; A CRITICAL STUDY OF SPECTRAL SERIES. 381 
limit is 30677 72 and may be taken as practically correct. That calculated from the 
series, and used in the preceding discussion is 30678‘93 + ^^. This, therefore, rei^iiires a 
correction of —1'21, The equations A would be satisfied by p = 1, dn = 2, —1'21. 
As however this value of ^ is probably correct within 1 the best value of Ag is 
obtainable from f{2), viz.. 
As = 4678-098 +-580 (r21 ± •!) +-086 x 1 ±'002 
= 4678-80±-10 
A's = 4242-18 ±06 
J = 249-536±-005. 
If the difference between ^ as found from i/j, z/g be real and depend on electronic 
changes as hinted at in the introduction, the changes calculate to 73-94 electrons = 74. 
In other words, the V 2 would refer to mass of nucleus +37 electrons and z/j to mass of 
nucleus —37 electrons. Is it merely a curious coincidence that the atomic number of 
Kr is 38, that of H being 1 ; all the electrons acting in one way for z^^ and in the opposite 
for z /2 ? it being remembered that when S lines are emittted one electron at least is 
absent. 
* Xenon — The X diffuse system appears to be a most complicated one. As we shall 
see later there appears to be a congery of series converging to limits which are 
collaterals of S (oo) = 51025, and connected with these there are again conoferies of F 
senes converging to limits collateral to the various sequents or, say, the normal 
F ( 00 ). These F series further show the existence of satellites—in other words the 
/ sequence is also subject to slight collateral displacements. This renders their 
disentanglement a very intricate problem not only in itself, but because it renders 
the region of the spectrum involved very crowded, with lines close together, with the 
consequence that coincidences occur which may not refer to real relationship. In fact 
there are cases where the calculated values of supposed lines of diiferent series are the 
same within observation errors.* This crowding is also increased by the existence of 
the allied F series referred to above. The complete discussion of all these related 
series should afford valuable material for arriving at a knowledge of displacement 
laws. Here it will be sufficient to indicate the nature of the problem and to deal 
with the material so far as to give confidence in the results as to the assignment of 
series and especially as to accurate determinations of the oun and the various links. 
As vacuum tube spectra approximate to the spark type, the difficulty of drawing 
definite conclusion from the existence of a triplet separation is again enormously 
increased by the presence of the link relations which these spectra show. In arc 
spectra the appearance of a z^j or separation may always with some certainty be 
ascribed to the fact that the lines in question are directly connected with series terms. 
A case in point is Fi (5) and F 3 (17) in the series next considered ; also + 3 ( 13 ) and F 2 (19). 
