XXX Proceedings. [Febmary 6th, igi2. 



disintegrating emits one a particle expelled with a definite 

 velocity, which is characteristic Oi the substance. In many 

 transformations, /3 and y rays are emitted, and from analogy it 

 would be expected that one /3 particle should be emitted for the 

 transformation of each atom. The experiments, however, of 

 Baeyer, Hahn and Miss Meitner, and ot Danysz, have shown 

 that the emission of /3 rays from the radio-active substances is, 

 in most cases, a very complicated phenomenon. The com- 

 plexity of the radiation is most simply shown by observing in a 

 vacuum the deflexion of a narrow pencil of /3 rays by a magnetic 

 field. If the rays fall normally on a photographic plate, a 

 number of sharply marked bands are observed, indicating that 

 the rays are complex and consist of a number of homogeneous 

 sets of rays each of which is characterised by a definite velocity. 

 The remarkable complexity of the /3 radiation is well instanced 

 by the experiments of Danysz, who found that the products of 

 radium B and C together emitted at least 27 sets of homo- 

 geneous rays. Some of these had a velocity exceedingly close 

 to that of light. Notwithstanding this apparent complexity, 

 general experiments have shown that the number of /3 particles 

 emitted from radium B and C is about that to be expected if 

 each atom in breaking up emits only one /3 particle. In order 

 to explain this complexity of the/3 rays, it is necessary to suppose 

 either that the atom breaks up in a number of distinct ways, 

 each of which is characterised by the emission of rays of 

 definite velocity, or that the energy of the /3 particle can be 

 reduced by certain definite amounts in its escape from the 

 radio-active atom. The latter view appears more probable and 

 more in accordance with the facts observed. It was found from 

 an analysis of the results given by Danysz that certain relations 

 existed between the energies of the individual /3 particles com- 

 posing some of the different sets of rays. The diff'erence in the 

 energies of the /? particles from radium B and from radium C 

 could be expressed by a relation of the form pa + qb, where a 

 and /'' were definite constants and / and q had integral values 

 o, I, 2, 3, &c. 



