Line-Spectra of the Chemical Elements. 



333 





Ca. 



Zn. 



ca. 



Vn 



223-2 

 1032 

 2-16 



876-5 

 388-4 

 2-23 



2483-8 

 1172-5 

 2-12 



V-, 



*>0 



v x 



These doublets contain the strongest lines of the elements 

 of group II. 



2. The corresponding components of the doublets form series y 

 of which the terms are functions of the consecutive integers. 

 Each series is expressed approximately by an equation of the 

 form 



n=n — -. ■ — ^ ; (1) 



where n is the wave-number, m any positive integer (the 

 number of the term), N — 109721 '6, a constant common to 

 all series and to all elements, n and /jl constants peculiar to 

 the series. It will be seen that n defines the limit which the 

 wave-number n approaches to when m becomes infinite. 



Messrs. Liveing and Dewar were the first to remark the 

 existence of the series, as well as their different appearances. 

 They are of three kinds : diffuse, sharp, and principal series. 

 The first two are formed by the above-mentioned doublets or 

 triplets ; in the elements of the groups I. and III. there are 

 consequently four different series of these two kinds, in the 

 elements of group II. there are six. I have named them 

 first, second, and third diffuse or sharp series. The lines of 

 the first series of each kind are the strongest and the least 

 refrangible. 



Hitherto I have found the principal series only in group I. 

 They are double, but the doublets are not of the same kind as 

 those described in section 1 ; the components approach each 

 other when m increases (see section 3). I name the stronger 

 of the two series, which is also the most refrangible, first 

 principal series. The principal series contain the strongest 

 lines of the spectrum (in group I.), then come the diffuse 

 series (the individual lines of which are in reality double ; cfr. 

 section 4), the sharp series are the weakest. In the individual 

 groups the intensity decreases as the order of the series 

 increases, in the same way as the lines grow weaker in the 

 individual series with increasing m. 



