CHAPTER XL 



FURTHER DISCUSSION OF THE ELECTRON THEORY 

 OF THE MAGNETISATION OF LIGHT AND DE- 

 TERMINATION OF THE m/e RATIO IN RADIATION. 



AMONG the early contributions that have been made 

 to the theory of moving charges, few are more 

 remarkable than those of Dr. Johnstone Stoney in 

 connection with the process of radiation, long before 

 there had been any experimental verification of the 

 separate existence of these electrons, or of the fact 

 that the emission of light from a substance is due 

 to their motion. Dr. Stoney had treated them in 

 an astronomical manner, in 1891, dealing with an 

 electron moving round an atom as if it were a 

 satellite moving round a planet, and had discussed 

 the various perturbations to which they might be 

 subject, and the effect of those perturbations on the 

 spectrum of the light emitted.* 



One of the simplest kinds of perturbation, fully 

 analysed by Newton for the motion of the moon, 

 is what is called a progression or recession of the 

 apses, being a slow revolution of the orbit in its own 

 plane. Such a motion was shown to be able to 



* " On the Cause of Double Lines and of Equidistant Satellites in 

 the Spectra of Gases." G. Johnstone Stoney, Transactions of the Royal 

 Dublin Society, iv., 1888-92, pp. 563-608. 



