the Spectrum of Copper. 465 



these, with extensions, before proceeding to the discussion 

 of the true F series d (1) — /(m). It may be noted in 

 passing that the existence of the D (1) set explains why 

 no F set was found on the old supposition, as only a 

 few lines of the combination d(2)—f(m) would be strong- 

 enough to appear. The material is given in Tables V— VII. 

 We will now discuss them in order, beginning with Randall's 

 allocations for ??i = 3. The data for the constant sequents are 



Pl (l) = 31523-48, d/(l) = 48962-91, d Y {2) = 12365-67. 

 p 2 (l) = 31771-92, d 2 '(l) = 49061*37, d 2 (2) = 12372-65. 



m 



= 3. The p-f (Table VII.) give f\ (3) = 6880*31 



/ 2 (3) = 6877-16. 



„ d (2) -/ (Table VI.) „ /,(3) = 6880-06 



/ 2 (3) = 6876-52. 



„ d 2 '(l)-f „ / (3) = 6880-12. 



The agreement amongst the sets renders the allocations 

 practically certain. But it may be noted as exceptional 

 that the f 2 sequent is less than the /i — i. e., it is a positive 

 displacement on f x contrary to the universal rule in 

 d satellites though not unknown in f. Further, in the 

 d 2 ' —f we should expect f 2 and not f\ as here. It is 

 natural to suppose that there is no / satellite and that 

 the d 2 (2) receives an extra displacement instead of /, 

 but this is negatived by the fact that f 2 occurs also in 

 the p—f line where this explanation is excluded. The 

 appearance of the j\ in the d 2 may be due to the fact 

 that in copper the D u line is scarcely formed and that 

 its place is taken by the undisplaced D 12 . On this sup- 

 position we should expect a double line dn = 3'2 or d\='2. 



Lines are also found corresponding to p 2 -\-f 2 and d 2 +f\. 

 The first, a spark line, gives />(3) = 6876*08 ; ihe lattev 

 / a = £885-8 -31 d\. 



The separation of fi(3), / 2 (3) appears as 3*54, 3*15, but 

 the measures are not very exact. A displacement of 6^8 

 gives a separation 3' 14. 



wi=4. The p—f are displaced by the electric field and 

 strengthened by it, as is the rule with this type of com- 

 bination. Stark's measures for zero field are used. These 

 give /i(4) = 4402-00, / , 2 (4)=4399'56. The summation gives 

 /; (4) =4402-00, / 2 (4) = 4399-68. The difference and sum- 

 mation thus agree with great exactness. They give as 

 the mean for ^i(l), 31523*475, thus closely supporting the 



