DR. W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 359 



drawn up on this basis. With these data, the suggested allocations for D, (2) give 

 I IK- following differences between tli.-ir denominators and that of D 13 (3), viz. : 



With D, 3 (2) = 29223 6528 = 9'5 x 683 



D lg (2) = -23254 267632 = 392 x 683. 



The first, therefore, cannot be a multiple within error limits. 



The values shown for D (4) agree very well, but the regularity is upset. Also the 

 actual lines have changed in appearance, and their intensities are not normal. The 

 intensities for D! (3) are 10, 6, 4, those for D, (4) 4, 4, 6. We should expect D n (4) to 

 be stronger, and certainly D, : ,(4) to l)e much weaker. It would seem that collaterals 

 must displace the normal lines. We have, in the foregoing pages, been led to expect 

 that an addition of an oun increases the intensity and a deduction diminishes it. If 

 so, we should expect a deduction in D n and an addition in D 13 . To bring D u 14<5 

 above D 13 requires the deduction to be made in VD. This would make the typical 

 value of the denominator greater by 2733, viz., 4'161071. In the case of D 13 , to 

 bring it closer to D, a , i.e., distant US, the addition would have to be to D(oo), and 

 if so, the value of 29<5, given in the modified table, would have been a mere coincidence. 

 But no such addition of a multiple of S (nor of <Jj) will do this. If, however, 2S be 

 added to the denominator in D ( ), it is brought to separation of 10<5+36, giving an 

 error in X for D 13 (4) of '02 in place of '06. If, then, S be also deducted from VD, 

 the separations will be 11(5. The separations would then take the form 



423(5 



US US 

 66S 



US US. 



This arrangement is to be preferred in that (l) it explains the abnormal intensities 

 of D (4), (2) brings the separations into line with other elements. The arrangement 

 suggested may be stated thus: if D u (4) and D I3 (4) represent the typical lines, the 

 observed D n is D u (4) ( 2<5) with decreased intensity, and D, 3 is ( + 2S) D, 3 (4) ( S), 

 the increased intensity due to the + 2S in D ( oo ) being greater than the decrease due 

 to -S in VD. 



The results for orders > 4 are similar to those of the other elements of their groups, 

 probably collaterals of additions to D ( < ). 



Zn. 



On account of the small values of <$ and the considerable observation errors, the 

 satellite separations in Zinc do not give decisive resulta If we take the observed 

 values for the D 12 and D 13 sets, the denominator differences are 489, 419 for m = 2, 

 .mil 584, 399 for m = 3. Now the second sets, the D.,, have much smaller observation 



