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



I am inclined therefore to think that the exact equality for ( + 9^) is a coincidence, 

 especially as the difference for m = 6 and 7 is not a multiple of A like the others. 

 Taking the corrected D(w) = 48163'62, the mantissa for m = 6 is '1 1(5154, giving 

 with M 13569 a difference 2585 = (l+) A-46, which is as far as it can l)e from a 

 multiple of A. 



If + 7S be taken for the collateral, and 5A for the difference, the limiting 

 denominator is '107384 and the corresponding O C are '03, +'03, '07. Now these 

 make, as against the observed D 3 lines, the values of v l about correct, which gives a 

 certain amount of weight to this arrangement of collaterals based on ( + 7S). 



In the foregoing the conclusions up to m = 6 may be taken as well based. No 

 definite answer can be given to the question of what happens beyond m = G, although 

 the balance of evidence perhaps points to the last, viz., collaterals based on ( + 7^), 

 and this is strengthened by considerations which follow. 



MANNING* has recently observed under diminished pressure certain groups of lines 

 which by their look suggest doublets and satellites related to the D type. The 

 strongest set, apparently a D n and D 2 doublet, are 4260'05, 4241 '25, giving a 

 separation of 104'05 ('5). If 4260'05 be treated as having the same limiting term as 

 the D series, the denominator of the VD part comes out to be 2107364 (21). Now 

 this mantissa has the limiting value according to the supposition of the preceding 

 paragraph, viz., 107384. If this is not a mere coincidence, the connection should 

 throw a great deal of light on the relations of these series, and would warrant a more 

 searching discussion. 



This would, however, lead too far from the immediate point at issue. It will be 

 sufficient merely to indicate somewhat more clearly the connection. With the limit 

 (7<J)D(oo) the mantissa of D 1 (7) is 299A below that of m = 2 (see Table II.), 

 and it should therefore be (with D (oo) = 48163'62) 631328 (25) -83-299A, 

 whilst that of MANNING'S 4260 is 107364(21) -42^. If these are the same 

 299A = 523964 (46) -41f 



A = 1752'388--14-15, 



and this gives S = 361'55< which is too small. But in this D(7) of the accepted 

 series is referred to (7$) D ( oo ), whereas 4260 is referred to D ( o> ). If it be referred 

 also to (7<5)D(oo), its mantissa is 107868 (21) - 



and 299A = 524468 (45) -41 



A = 1754-073'15--14 

 and therefore of the right order with $ = 36T89W 2 . 



MANNING'S new lines suggest, on a superficial glance, a series of bands, but there 



-tie doubt of their connection with the Diffuse series. Their relations to one 



another can be discussed either on the basis of the old D ( oo ) or of (7$) D ( oo ). With 



Observed in my laboratory, since published in ' Astrophys. Joura.,' May, 1913. 



