



Proceedings of the Royal Irish Academy, 



opectr. Line. 



n calc. 



n obs. 



calc. 



S obs. 



B 



1-5319 



1-5319 



0-515 



.. 



C 



1-5336 



1-5335 



0-573 



0-573 



B 



1-5386 



1-5383 



0-745 



0-758 



E 



1-5454 



1-5452 



0-990 



1-000 



F 



1-5515 



1-5515 



1-226 



1-241 



G 



1-5636 



• 1-5639 



1-723 



1-723 



H 



1-5744 



1-5744 



2-206 





These constants given by Drude, if they are reduced to the proper 

 units, enable us to calculate g'/r by means of equation (5). The 

 calculation possesses no special interest, and is presented separately 



in I^'oTE E. The calculation shows that is constant, which 



Til 



follows from the fact that Verdet's constant is independent of the 

 magnetic field. It is assumed in the foregoing that all the ions in 

 any one absorption-band describe circuits of the same area and period ; 

 since these ions are all alike in their properties, this must be true, as 

 they should behave similarly in the magnetic field. 



From Drude' s constants we get for the ions in the ultra-violet 

 absorption-band of carbon disulphide and creosote the following values 

 J_ ._ 



for 



3-87 X 10 ^ for carbon disulphide. 



^ = 4-28 X 10-5 for creosote. 



It would thus seem that we could determine the area and size of 

 these ionic circuits for a given magnetic field when the value of t is 

 known, and thus get an estimate of the internal motions in the 

 molecule. 



The Period of the Ionic Circuits. 



In deducing this result, no conception has yet been formed regard- 

 ing the mass or period of the ion. It would seem natural at first to 



