PROF. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 89 



From analogy with the preceding elements it is natural first to seek for the 

 presence of a series whose limit is VD (2). This is 



24467-09277-12199-582 = 12267'514-77. 



The lines 18459, 12677 fall in with this, but no others of the series have been found. 

 If the limit is actually 12267 the formula can be found at once. In all the other 

 cases, however, it has been slightly different. It will, therefore, be best to use the 

 old RYDBEEG formula, whence 



n- 12275'3-N/(m + -998613). 



The next three lines given by this are X = 10837, 9963, 9469, but these come in a 

 region in which there are no records. It is below BERGMANN'S lowest and SAUNDERS' 

 highest. The limit falls about 8147, close to 8210, where SAUNDERS observed a faint 

 group. The latter might, therefore, represent the last faint lines visible. 



The four lines above these in the list are doublets v = 5'543'28 and 5'50'92. 

 PASCHEN points out that they satisfy the relations V?! (2)-VD (3), VP 2 (2)-VD(3), 

 VP!(2)-VS(2), VP 2 (2)-VS(2). To test this, as in the case of K, P() is 

 41446-761'69, P 1 (2) = 30271'83 "27, P 2 (2) = 30266'33'27, D( oo ) = 24474'133-48, 

 D 1 (3)=l7575'28-46. Hence VP,(2)= 11174-93 + 1-96, VP 2 (2) = 11180'43 T96, 

 VD(3) = 6898-853'94, VS(2) = 15705'694'G1, whence the wave-numbers com- 

 pared with observed would be 



Gale., 4276-08 + 8-90, 428r588'90, 4528'266'57, 4530'766'57 ; 

 Obs., 4273'98l-82, 4279'52r4G, 4526-940'51, 4532'550-41. 



Here also, contrary to the case in K, the test as to doublet separation holds. The 

 observed v for the P(2) lines is 5 < 50 + '54, agreeing with the separations in this case. 



The lines marked with A in the list form a doublet series v about 14 '7 which 

 has been called LENARD'S series, who first discovered some of the lines, later measured 

 by K.H. and by S. The lines were arranged in the above order by SAUNDERS, who, 

 however, could not fit in any of the usual formulae for it. The readings are too 

 uncertain for any definite assertion. If the first three corrected to constant v = 14 "8 

 be used to determine the constants, each of the second doublet being means of K.H. 

 and S., the resulting formula is 



n = 24570-6 - N/(m + l'013864 + r 1 x 281906), 

 85-4 



giving the following values for obs. calc. : 



m = 2 3 4 5 6 7 



o --1 1 2-5 



VOL. OCX. A. N 





