84 



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



constants, forms another argument in favour of the view that Rb and K actually do 

 not possess satellite series like Cs. They have not been observed not through the 

 observer's fault, but because they do not exist. 



The limits of errors are so much wider in the case of these series than in that of 

 the P that the evidence in favour of the above is not, perhaps, so conclusive as for 

 the latter. I think, however, that there can be no reasonable doubt that it is correct 

 in the main. It is quite possible that, in place of unity from which the terms are 

 deducted, the true quantity may be a number near unity for the alkalies. 



The values of are so uncertain that it is hopeless to expect to draw any safe 

 conclusion from them, beyond this that apparently the simple law observed in the 

 case of the P series does not now bold. For K the value of D is very close to 



For Rb it may be written 



m 



m 



l 



For Cs the a is verv small for both satellites and practically equal, the D's differ 

 only in /A. The constitution of a for 1) must therefore, unfortunately, with the 

 extremely, inexact measurements, be left unsettled at present. 



Other Associated Series. 



In discussing the remaining observed lines of the alkalies not included in the three 

 typical groups, it will be simpler to take the elements in the reverse order, commencing 

 with Cs. 



Cs. The lines to be accounted for are the following, in which the letter refers to 

 the observer : 



In the above v denotes the difference of wave-numbers of the lines above and below 

 it, the top line being taken when two observers are in question. The pairs are 



