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 = 30. are given in the table and the notes thereto. There are 
certain lacunm—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 ra — 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 ni = 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 Fj (l) must be in the neighbourhood of 3100. The matter can only 
l)e 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 vacuo of 332187 A.U. The mantissa of 3010 -I- rin with the limit 30725'26-1-f is 
9892854-35'9 {dn — ^) = 90 {10998'8 —'If-l-'Idn} —611 = 9 OA 2 —The uncertainty 
in A 2 as found from i >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 
Aa 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 m = 1. With the value of A 2 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'j 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 r25 in m = 2, and '50 in m — 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 Au, the F and D linkages 
show a preponderance of the a, h, c, d links, and no doubt fuller evidence might have 
been adduced by using them, Init 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 (l) 20581'64, 1864*85 (R) 22446‘49, are 1973‘85, above F^ and F^-t-i'], or the real Fg. 
The two lines (5) 23268'21, ( 2 ) 82'67 are respectively + 6^1 displacements of 23275*44 
which is 1875*23 (or c) above the observed Fg or 1873*15 above the normal value 
Fi + J'i-t^a- For m = 3 we find ,, 
