,;. w. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



riven the values of O-C least. If ( be taken about '6, the order differences can run 

 3A . 4A, 4A within error limits. 



K. 



It is seen that the numbers, with the exception as in other cases of the first 

 difference, fall into multiples of A quite naturally without a change in D ( ), though 

 possibly a' small change in might make the values of O-C less. A is so large, that 

 the theory of the dependence on multiples receives considerable support. The first 

 also is close to 20A. This element is one in which the value given in the first 

 discussion above for the oun is 862'68tc, which is presumably too large by '8 to "9. 

 If it be 361'8, A should be b less and = 2933. This would scarcely effect the other 

 intervals, but it would make the first one = 20A-704. Again there is a sudden fall 

 (at m = 8), It doubtless corresponds to a real effect, for SAWDERS as well as 

 LIVEINO and DEWAR make anomalous here. S. observes * = 61'25 and L.D. 59'15, 

 hut both give D,(8) the same. If this be taken as correct and the normal D t (8) 

 found from D-,-57'87, the mantissa is 733756, giving the same difference 2A. This 

 shows that the D a set have not participated in the sudden fall at least to the same 

 degree as D, a result analogous to what happens in Na. 



Eb. 



In Rb there is some doubt whether a satellite series exists. The question has 

 already been discussed in [I., pp. 71, 86]. SAUNDERS has given for D (3) lines whose 

 wave numbers are 12883'93, 12886'56, and 13121'19, with normal separations 237'26, 

 and satellite separations 2 '6 3. Also D (4) is a doublet having a separation 23 5 '52, 

 which certainly points to an unobserved satellite about 2'4'l. But RANDALL'S 

 observations for D (2) show only a doublet of normal separation that is clearly with 

 no satellite. Moreover the F series, which depends on D n (2) and D J2 (2) for its 

 limits, is a singlet series and not a double one. In the table the series is taken as if 

 it were without a satellite, the reading for D t (4) being corrected from D 2 (4) v. In 

 other words it represents the satellite lines if they actually do exist. In the latter 

 case the strong lines would show denominators about 609, and 1100 above those in 

 the table for D u (3) and D n (4). The first is about 28 and the second of the order of 

 4cJ, whilst if normal, judging from other cases, they should be equal. Moreover, in 

 all other cases (In and Tl excepted) the satellite separations are practically the same 

 multiples of the oun in the same group. Cs shows a difference of 14^, so that the 

 supposed ones here are far too small, as well as irregular. The observed separations, 

 moreover, are equal within errors of observation, which would rather point to an 

 alteration in D, ( t ). Now a lateral displacement of 2S on D ( o> ) would produce a 

 separation of 2 '41, which is about the observed value. 



The table shows a stationary point at m = 8 and 9 and then the large fall shown 

 in the other elements. They could be accounted for by a lateral displacement 



