460 Prof. E. Rutherford on the Origin of 



radium C in one gram of radium is about 8 gram calories 

 per hour. Supposing, as Moseley found, that one ft ray is on 

 the average expelled from each atom of radium C, the energy 

 emitted per atom of radium G in the form of ft and 7 rays is 

 17*8 x 10 13 e ergs, assuming that 3*4 x 10 10 ft particles per 

 second are emitted from radium in equilibrium with 

 one gram of radium. This approximately corresponds with 

 the average energy of the ft particle included in group 

 No. 22, viz. 16-6 xl0 13 £. 



Danysz states that No. 22 consists of 3 to 5 groups of 

 ft rays, for which only the average velocity of the group is 

 given. In the absence of any definite information of the 

 velocity of the components, it is impossible to ascertain 

 whether any relationship exists between this complex group 

 and the rest of the radium C series. The wide difference 

 between the energies of the ft rays included under No. 21 and 

 No. 22 indicates that possibly a third region exists within 

 the atom for which the energy required to excite 7 rays is 

 much greater than that for the other two regions considered. 



Unless the energy of the ft and 7 rays from radium 

 determined by experiment has been much underestimated, it 

 does not seem possible to suppose that the swiftest ft ray 

 given by Danysz, which has the energy 27 x 10 13 e, can be the 

 head of the ft ray series. The existence of such a swift group 

 of ft rays is, however, open to some doubt, as Danysz expressly 

 states in his paper. The photographic effect of such swift 

 ft rays is very difficult to detect in the presence of a strong 

 photographic action due to the y rays. 



We have so far confined our discussion to the connexion 

 between the ft and 7 rays emitted from radium 0, for in this 

 case the necessary data are far more definite and complete 

 than for any other product. It seems probable, however, 

 that the same general explanation will apply to the emission 

 of ft and y rays from mesothorium 2 and thorium D, both of 

 which emit a number of groups of homogeneous 6 rays and 

 also penetrating 7 rays. In each of these products, the 

 energy emitted in the form of 7 rays is of about the same 

 order of magnitude as the energy emitted in the form of 

 /3rays. 



A difficulty arises in connexion with the ft ray products 

 like radium E and uranium X, which emit penetrating 

 ftrays but relatively weak 7 rays. In the case of uranium X, 

 some penetrating 7 rays are observed, but they are weak in 

 relative intensity compared with the 7 rays from radium C. 

 It is possible that the atomic structure of uranium X is such 

 that only an occasional ft particle loses energy by conversion 



