DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERO& 419 



D (2). The lines in the far ultra-red have since been observed by PABCHKN (' Ann. 

 d. Phys.,' 33, 1910, p. 717). BERGMANN'S lines began with the order m == 4, but in 

 the lists above more recent and more accurate measures by others have been inserted. 

 BN. refers to BERGMANN, RL. to RANDALL ('Ann. d. Phys.,' 33, p. 741), 8. to 

 SAUNDERS (' Astrophys. Journ.,' 20, p. 188). 



In 1905 FOWLER ('Astrophys. Journ. ,' 21, p. 84) discovered the lines in the F 

 series for Sr, beginning with K.R.'s 4892, adding two sets of his own observations 

 and "also the two connected triplets given in the table. But he attempted to combine 

 them all in one formula. The disarranged triplet for m = 3 is assigned in the text 

 above from K.R. and LKHMANN (' Ann. d. Phys.,' 8, p. 647). In the same volume 

 SAUNDERS (' Astrophys. Journ.,' 21, p. 195) added the last line and gave a similar 

 series for Ca, commencing with 4586. The measures inserted in the table, however, 

 are from later observations by BARNES (Bs.) (' Astrophys. Journ.,' 30, p. 14). 

 SAUNDERS also suggested a corresponding series for Ba in which the separations are 

 larger than those of the series assigned in the text. It is possible they may form a 

 similar series connected with the enhanced series. The lines for RaF and allied sets 

 are assigned also in the text above. 



The F lines for Mg, Zn, Cd, Hg, Al, and Tl are all due to PASCHEN (' Ann. d. 

 Phys.,' 29, p. 651, and 35, p. 860). In Hg, however, he assigns 17195 to a combination 

 line, whereas in the text above it is assigned to F,. 



[Notes, September 2, 1913.] 



Note 1 -Since the present communication was read Messrs. FOWLER and REYNOLDS ('Roy Soc. Proc., 

 89 p. 137) have published more accurate and extended measurements of the series, and other linen 

 The limit of the D or S series appears to be somewhat higher than that adopted in thu Table I 

 and the table will require the limit to be slightly raised to bring in multiples of A for the order d 

 With FOWFER and REYNOLD'S limit the mantissas show rising values for the first few o 

 decreasing an effect which has been explained in the text in similar cases by a collateral d.splaccracn 

 the limit after a particular order. If the limit be taken to be 39757-78 (i.e., 6-7 higher than in t 

 there results an order difference of 4A 3 between m = 2 and 3, and equal mantissa, nfwrwar 

 = 9, when there is a sudden change to a rising. If the limit is now raised by unUy for t 

 mantissa can again be all equal. Now, a displacement of 3 on the limit makes a change o 



3 H 2 



