464 Prof. W. M. Hicks on 



those giving d}. The calculated and observed combinations 



then give 



Calc. Obs. 



7//-- r /-.n oa^o Vo( (1)20640-47 Exner and Haschek 

 4'(l)-4(l)-20643-48| ( y 2Q639 . 69 Hasbach 



^'(1) _ J 2 (l) = 20545-22 (2n) 20543-50 ±'85. 



There is also a line by E.H. (2) 20574*25 ±-85 which 

 if it is the combination dV(l) — d x {l) gives a — 30*75. 

 With 133 A, 



d 2 (l) =28207-43 + 1-25 f, 

 D 12 (l) = 3316-05 --25? 

 D 12 (l) = 59730-91 + 2-25f. 



There is a line (7) 59719*32 — 35'6dA, which would serve as 

 a D n giving a=ll'6 + 35d\. It is so strong that we should 

 expect that at least D 22 should be visible, but there is nothing 

 which can possibly stand for it. The combinations are 



Calc. Obs. 



d 2 ! (l)-d 2 {l) = 20853-94 (2w)20852-66, 

 d 1 '(V)-d 2 {l) =* 20755-61 none ; 



and again 20767*6 (a spark line observed by Hemsalech) can 

 serve as d\(\) — ^(1) giving cr = 12, or the same as by the 

 direct summation lines. Little weight perhaps should be 

 given to this case, but so far as it goes it points to a second 

 system of D series. 



That part of Handke's observations which lies beyond 

 \ = 1770 shows clear evidence of connexion as summation 

 lines with D(l) sets, depending not only on different 

 d 2 sequences, but on displaced d sequences and displaced 

 D(co) limits — a short discussion of them is given in the 

 Appendix. 



The F series. — So long as D (2) was believed to be 

 the first set in the D series it was natural to attempt 

 to allocate F series with limits = di(2), ^(2), with therefore 

 a separation of 6*98. No such doublet series were found. 

 Nevertheless Randall proved the existence of certain se- 

 quents with all the appearance of belonging to the F type. 

 The proof depended on the existence of lines satisfying 

 the conditions for combinations p(l)—f(m) d'(V}—f(m) 

 and one doublet set d(2)—f{3) far up in the ultra-red but 

 with a separation 10*5 instead of 7, thereby indicating 

 n satellite effect in the f sequence. We will consider 



