SCIENTIFIC HYPOTHESIS 251 



THORIUM a 



MESOTHORIUM 1 no rays 



Mesothorium 2 p + y 



RADIOTHORIUM a 



Thorium X a + p 



Emanation a 



Thorium A a 



Thorium B slow ft 



Thorium C { * a 



( C 2 a 



Thorium D 



ACTINIUM no rays 



Radio-actinium a + p 



Actinium X a 



Emanation a 



Actinium A a 



Actinium B slow 3 



Actinium C a 



Actinium D a + y 



