DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 359 



Here again the links to the line observed near normal S s are bad, whereas the links treated as good refer 

 back to a line exactly i< 2 ahead of S 2 . Further the 12 or 6 separation is again in evidence. Also the links 

 2e, -2e + u, -e-u refer back to lines differing by about 6 from S 2 . 



8(4). 



[45179-30] [45358] [45434-40] 



u(l) 45618 --02 -(!) 45635 -00 --(!) 44996 --09 



-v (4) 44735 -07 - v (3) 44913 -12 -e-(l) 44275 --01 



-2 + t>{2) 44175 --16 



Here the calculated lines agree remarkably with the sounded. The calculated are therefore adopted. 



S(5). 



[47501-68] [47681-18] [47756-78] 



(1) 48126 --12 

 w + 6(l) 48126 -00 



The only links apparent are for So, again with the 6 displacement. These lines are all close to the limit 

 of observed region. 



S (6). 



[48776-74] [48956-34] [49031-94] 



-2e + fl(l) 47784 -10 - 1e- 12 (1) 47522 -09 -e + w(l) 48753 '00 



-LV -)<(!) 47155 --10 



The lines are now so far out of the observed region that the links are too small to refer back to well 

 observed regions even if such lines are really existent. 



The foregoing discussion of the S series affords evidence of the existence of dis- 

 placements of about 12 (or 6). This requires further consideration as affording 

 material on which additional knowledge may be obtained regarding the laws which 

 such displacements follow. The presence of the same displacements in successive 

 terms of the series points to a modification on the limit either a pure displacement, 

 a linkage effect, or, as the separation is small, possibly the difference of two links. 

 The further evidence to follow points decisively to the existence of displacement. 

 Whether they are due to displacements by multiples of the oun on the limit is, of 

 course, not so convincing. The numerical relations are very closely represented on 

 this hypothesis, but in the case of argon the S l is so small that it produces in 8, 

 separations of 1'03 only. In lines whose wave-numbers lie about 40,000 or greater, 

 this produces, changes in X of '06 and therefore comparable with observation errors. 

 In the case of 8 (2) only wave-numjbers of order 26700 does it produce d\ = '15. 

 The measurements here are by KAYSER, whose errors are probably < '02, almost 

 certainly < '05, and a close agreement between calculated and observed lines will 

 give evidence of some weight. 



VOL. ccxx. A. 3 D 



