:; .-.,. DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



He. Limit given in [I.J which is practically exact, v = 1 -007 is given by PASOHEN as a result of all 

 hia readings and is probably not more than '002 in error. Consequently, the numbers for He have weight 

 in spite of its low atomic weight. 



0. The limit is 23204-00. Although v } , v 2 are known with fair accuracy, the possible proportional 

 errors are considerable, so that the data have small weight. The limit for the doublet series is 21204 with 

 v = 62. The values are still more indefinite. 



S. Limit 20106. The D series give 20110. This gives a considerable range of uncertainty. 



Se. Limit 19275-10. The atomic weights for 0, S, and Se are those of the International Committee 

 of 1910. 



The table shows at once that the two groups which give doublet series agree in 

 giving the A as multiples of a number close to 861'Sw 1 . Group II., giving the triplet 

 series, require in several cases multiples of 9CH0 2 or 180w 2 . It is curious that the 

 groups which first indicated this relation do not show it so markedly and with so 

 little doubt as the doublet series, in which by themselves it would probably never 

 have been noticed. There seems to be some kind of displacement with the middle 

 lines of the triplets. If, for consideration, the values of A^Aa be taken, this 

 irregularity disappears, and, moreover, with the larger observed quantities, the 

 proportional errors will be less. 



If we agree to look upon the 361 as the normal type, and for numerical comparison 

 multiply the 90 by 4 and the 180 by 2, and, if further, the results are supposed to be 

 weighted by the estimated limits of variation assigned in the last column of the 

 table, the method of least squares gives for the value of q = S/w 2 



Group 1 361-900, 



,, II 361720, 



HI 362-051, 



All three groups 361'890. 



In Groups II. and ILT. it is possible too much weight has been given to Hg, v a , and 

 Tl. We will take as the preliminary value for q that of silver, viz., 361 '81, which is 

 practically that of the general weighted mean. The true value cannot vary much 

 from this probably less than '2. With this, the subsidiary values become 180'90 '1 

 and 90'45 '05. 



It is seen that in the doublet groups all the elements can come within this limit. 



In fact, with the exception of K and Ga, they come extremely close. Ga is 



spectroscopically uncertain as well as in its atomic weight, and the uncertainty of K 



s due to the uncertainty in its value of . In the triplet groups also, all calculated 



from A, + A S have possible variations which will bring them within, although the 



not so marked as for the doublet elements. The sequence formula 'are 



itablished in Groups I. and III., but there are uncertainties in Group II. which 



equire clearing up. In this relation also, the table shows slight regular variations 



as, e.g., A, and A s err from the general mean in different directions, but in these cases 



