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



The lines of the series seem to be exceptionally numerous. The results of the 

 examination up to m = SO are given in the 'table and the notes thereto. There are 

 certain lacunae especially for m = 4. In these cases however corresponding displaced 

 sets are in general observed, and naturally with large values of m this effect is more 

 frequent. In certain cases where a set is absent a parallel set is observed linked to 

 the normal type. This is the case for instance in m = 4. 



The question naturally arises whether lines exist for m 1. If so the formula gives 

 a triplet with the first line at n = 3142, far in the ultra-red. In other spectra these 

 values extrapolated for m = 1 differ considerably, often by several hundreds, from the 

 correct ones. We can only conclude that if there are sets based on m = 1 they 

 must be such that F, (l) must be in the neighbourhood of 3100. The matter can only 

 be settled therefore by other considerations which must depend with our present 

 knowledge at least either on sounding or on the presence of combination lines in 

 the observed region. The evidence for such a triplet is given below in the notes to 

 the list of lines. The value of F, (l) found is 3010'35 corresponding to a wave-length 

 in vacua of 332187 A.U. The mantissa of Wl() + dn with the limit 30725'26 + is 

 989285 + 35'9 (dn-f) = 90 {l0998'8-'4f+ '4d/t} -611 = 90 A,- The uncertainty 

 in AJJ as found from v. 2 is too large to settle the exact value of this with so large a 

 multiple as 90, but the fact as it stands that the mantissa differs from a multiple of 

 A 2 by only a few ouns is what is to be expected if the series belongs to the F type, 

 and so far certainly supports the more direct evidence given below for the existence of 

 the set depending on in = 1. With the value of A a found below dn = 1'5. 



A glance at the list will show that the separations observed in the second and third 

 orders of F are less than the normal values. This points to a satellite effect. The 

 values of i/, are 1862'96, 1863'92 which show deficits of 1'54, '58 from the true value 

 as indicated by the occurrency curve. Now a displacement by one oun produces a 

 change of 1'25 in in = 2, and '50 in in = 3. The deviation is then completely 

 explained by the supposition of the existence of the satellite effect depending on <$,. 

 The 1/2 show similar deficits, which may possibly be due to observation errors. We 

 should expect to find a similar effect (not necessarily the same multiple) in the order 

 m = 1. In this order the oun produces a change of 4'25. 



For sounders and for link evidence the data have been restricted to e, u, v links 

 only. If we may judge from the examples of Ag and An, the F and D linkages 

 show a preponderance of the a, I, c, d links, and no doubt fuller evidence might have 

 been adduced by using them, but it was necessary to set limits to the work, as well as 

 to this communication which is long as it stands. But as examples we may give some 

 d links belonging to the orders 2, 3 of F,. The value of d is 1973 '94. For m = 2 the 

 lines (1) 20581-64, 1864/85 (3) 22446'49, are 1973'85, above F t and F^i/,, or the real F a . 

 The two lines (5)23268'21, (2) 82'67 are respectively +6<5, displacements of 23275'44 

 which is 187 5 '23 (or c) above the observed F 3 or 187315 above the normal value 

 F! + 1/! + i/jj. For m = 3 we find 



