766 



Prof. A. H. Compton on the 



Since the speed of even the swiftest alpha particles is only 

 about one-tenth that of light, it is clear that the radiating 

 particles cannot have mass comparable with atoms, but must 



Fig. 2. 



4500 



4-000 



3500 



3000 



2500 



2000 



1500 



1000 



500 



be individual electrons. We are thus led to the idea that it 

 is the vibrations of the secondary beta particles themselves 

 which give rise to the fluorescent gamma rays*. 



* The corresponding hypothesis that the "white radiation" from an 

 X-ray tube is due to vibrations of the cathode particles has been sug- 

 gested on the basis of similar considerations by D. L. Webster, Phys. 

 Kev. xiii. pp. 303-305 (1919). 



