the Spectrum of Copper. 477 



mantissa consequently decreased. This decrease is found to 

 be 186*9 #. Hence to get the multiple law 



186-9*=1536 — 38# + /o 



where p is an unknown correction due to incorrect value of 

 N and certainly less than 260. Hence 



.i« = 8*2-*20?/ + l-37. 

 If there is no N correction <r = 8 or x=7 with ?/ = 6. Hence 



d 2 (l) = 58281-9 +#-31523*48 + 4-94.r = 26758-4+y + 4-94a, 

 now 



.^/(l) = 49061-37, ^' = 48962*91. 



Hence 



d 2 '-d 2 = 22302*97-#-4*94.r =22262*45 



rf 1 '-d 1 = 22213-37-#-4-94tf = 22173*8 



di'-rf, =22164-1 



The only lines in this neighbourhood are (2 n) 22252*85, 

 (In) 22188-25 spark lines by E. V. and (2 w) 22150*21, 

 (4)22168*82, (6rt) 22178*56 arc lines. The two last differ 

 by 9*74, the mean satellite separation as found from the last 

 three sets above. They clearly belong to the d\ — d 2 > di' — di 

 combinations. The spark line 22188*25 is 9*69 ahead of 

 22178*56 and will correspond to a second satellite displace- 

 ment of the same amount as the normal. The differences 

 between the calculated and observed will depend on the 

 ■effect of incorrect N. The further discussion is therefore 

 deferred, but the set provides material for the discussion of 

 the N effect and is of importance for this reason. But the 

 five systems also support the evidence already adduced that 

 several independent D systems exist — at least for m = l. 



(4). In searching for F(2) lines which should show a 

 separation of about 25 and lie in the region of wave numbers 

 about 16000, whole sets were seen with this separation 

 scattered over a wide area and showing a large number of 

 the p links. These are sure signs of F regions of low order. 

 As material illustrating this the following examples are 

 shown. The wave numbers are in I. A. calculated from 

 wave lengths of Aretz given to *001 A. The separation 

 values are therefore very exact and might therefore well 

 repay a more detailed investigation of their relations. 

 Double displacements are clearly present and the 248- 

 separations are links : — 



