DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 395 



differences of the denominators of F n (m)-F( m+ l) is always the same multiple of 

 A 2 , as ,s done below. The line 19897 has separation 689-33, and therefore should 

 have a satellite (too faint) 16"60 above it. Allowing for observational errors on 

 197 this is 5* on the denominator. The following scheme will then illuHtrate the 

 law of formation : 



Calculated F 13 (2) 2'868676 



Satellite 



17165-94 

 17236T.8 



17300-80 

 Satellite 



19897-05 

 21350-92 



3-837028 



3^8 



3*843521 -258'8 

 S'861964-262-6^ 



98 

 3'878913-266M 



4*825655 

 4' 8 30 49 2 

 28 

 4-834202-515^ 



5'818813-898'2_ 



-993288 = 29(34251 14-9-05^), 34296 14 



993464 = 29 (34257 -4- 8 -8), 34301 



993158 = 29(34246'8-13-2), 34312 



In the above the first is the denominator calculated from 937300-2A a . It is 

 affected with an uncertainty of about 400 on the 937300. The line n = 17165'94 

 has a separation 680'84 with 1784678, and therefore should have a satellite 25'09 

 above it. Its denominator difference is 6493 behind and 3<? = 6492. The line 

 17236 '68 is associated with 17300. Its denominator is 16949 behind that of 17300 

 and 9<5 = 16695 the same within limits. The satellite of 19897 is displaced 4$<J. 

 There is no evidence of a satellite 2S behind it, but the difference of 29A a is made 

 with this suppositions one. It is seen that a value of about 5 makes these the 

 same within limits. The corresponding values of A a are appended in the last column. 

 It may be taken that the discussion has established, that the satellite differences 

 in the lines EaD(2) are 16(5 and IOS. This is the only result of which there can be 

 certainty. 



The Zn Sub-group. Using the limits given in Table II. above and the corresponding 

 values of D l (2), the limits F, ( ) = D ( oo ) D n (2) come as follows : 



Zn 

 Cd 

 Hg 



12988*37, with separations 4'88, 374. 

 13022-83 18-23, 1T10. 



12753-07 



34'68, 62-04. 



3 E 2 



