xviii Proceedings. [March gth, 1915. 



beta rays which are emitted with gamma rays. A large number 

 of lines were observed in the spectrum over a wide range of 

 wave length. Two well-marked lines are reflected from rock 

 salt at io° and 12 , and correspond to some soft gamma rays. 

 There were other strong lines of i° and 17 , corresponding to 

 the very penetrating rays. The shortest wave length observed 

 was '07 Angstrom unit, which is about 1/50000 of the wave 

 length of visible light. This radiation has much the shortest 

 wave length at present known. 



An account was also given of the methods for determining 

 the magnetic spectrum of the beta rays. For this purpose, the 

 rays from a fine source, passing normally in a strong magnetic 

 field, describe a circular path and fall on a photographic plate. 

 Under these conditions, a number of well-marked lines are 

 observed on the photographic plate, which correspond to groups 

 of rays of definite velocity. The speed and energy of the beta 

 particle comprising each of these groups of rays from radium 

 products have been accurately determined by Rutherford and 

 Robinson. The general evidence indicates that there is a very 

 close connection between the emission of beta and gamma rays 

 from radioactive bodies, and that the energy of the groups 

 of beta rays are intimately related with the frequency of the 

 gamma radiation from which they arise. 



An account was given of a general theory to explain the 

 connection between the beta and gamma rays. It is supposed 

 that the breaking up of an atom is accompanied by the expulsion 

 of a swift beta particle from the nucleus. This beta particle in 

 escaping from the atom sets the external electrons in rapid 

 vibration, and gives rise to the gamma rays observed. The 

 radiation from the disturbed electrons may be given out either 

 in the wave form or as swift electrons, and these two forms of 

 energy are mutually convertible. Evidence was also given that 

 during the disintegration of an atom, the beta particle is always 

 expelled in a certain definite direction with regard to the 

 structure of the atom. It was pointed out that the emission of 

 beta and gamma rays from radioactive substances must be 





