1901.] 



and Melting Points to Atomic Mass. 



19 



which form doublets. The differences in oscillation frequencies 

 between these doublets are not constant, as in the doublets of the 

 subordinate series ; they diminish as the refrangibility increases. 



The lines corresponding to the following values of m were known 

 when this part of the work was done : 



Lithium 1 — 9, sodium, 1 — 7 ; and potassium 1 — 9, rubidium 1 — 4, 

 •caesium 2 — 7. 



The differences between the observed and calculated numbers, when 

 Kydberg's method is used, are given in the following series of potassium. 

 The lines m = 2 — 7 were used to calculate the constants ; the line 

 m = 1 was omitted, so that the constants might be compared with 

 the corresponding constants of rubidium and caesium. 





Calculated 



Observed 





m. 



number. 



number. 



Differences. 





io 8 x- 1 . 



10 s x- 1 . 





1 



13584 



13042 



+ 542 



2 



24719 



24719 







3 



28991 



29006 



- 15 



4 



31069 



31073 



- 4 



5 



32233 



32226 



+ 7 



6 



32950 



32940 



+ 10 



7 



33424 



33409 



+ 15 



Similar results were obtained with all the principal series: the 

 differences increased slightly with the atomic mass. 



Several lines have been measured in the oxyhydrogen flame spectra 

 of the elements — potassium, rubidium, and caesium. The results are, 

 in some cases at least, more accurate than those of Kayser and Eunge : 

 the differences between the measurements of the same lines on different 

 plates are smaller than the limits of error given by them. Some of 

 the lines have not been measured before. 



The oscillation frequencies, reduced to their values in a vacuum, 

 were used in the following calculations, and the value of N (109675) 

 -corresponding to this reduction was also used. 



The chief points to be noted in the calculations are as follows : — 



The value of the limit of the series diminishes as the refrangibility 

 of the line, from which its position is calculated, increases, until an 

 almost constant value is reached in the lines corresponding to values 

 of m greater than 4. These lowest and almost constant values are, there- 

 fore, nearest to the true limits of the series. 



The spectra indicate that the value of n x must be the same for 

 both series : — 



C 2 



