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XXXIV. Deviahle Rays of Radioactive Substances. By 

 E. Rutherford, M.A., f).Sc, Macdonald Professor of 

 Physics, and A. Gr. GrRlER, M.Sc, Demonstrator in Physics, 

 lie Gill University. 2 font real *. 



§ 1. npHE experiments f of Giesel, Becquerel, Curie. 

 _L Meyer, and Schweidler have shown that radium 

 gives out some rays deflectable by a magnet. 



Becquerel, in addition, has shown that uranium, and the 

 excited radioactivity due to radium, also emit rays deviable 

 by a magnetic field. Becquerel has employed the photo- 

 graphic method for detecting deviable rays, while the Curies, 

 Meyer, and Schweidler have used the electrical method for 

 analysis of the deviable rays from radium. 



Further experiments have shown that these deviable rays 

 are similar in all respects to cathode-rays. Dorn J showed 

 that they were deflected in an electrostatic field, while the 

 Curies § showed that they carried with them a negative 

 charge. Becquerel determined the velocity of these 6i elec- 

 trons " by observing the magnetic and electrostatic deviation 

 of the rays. He found that the rays from radium were 

 complex, and had widely different velocities. Some travelled 

 at more than half the speed of light. The ratio of the charge 



to the mass — was found to be about the same as for cathode- 

 m 



rays. These results have recently been confirmed by Kauf- 



mann ||, who has shown that some of these electrons travel 



with a speed nearly equal to that of light, while the ratio of 



— is somewhat less than for the comparatively low velocity 



cathode-rays, and appears to decrease with the velocity of 

 the electron. This points to the conclusion that for these 

 high-speed electrons a portion of the effective mass is elec- 

 trical in origin %, 



The authors have found that, in addition to uranium and 

 radium, thorium compounds, and also excited radioactivity 

 due to thorium, give out some rays deviable by a magnetic- 

 field. 



* Communicated bv the Authors. Communicated to the American 

 Physical Society, April 21, 1902. 



t See reports on radioactivity by Becquerel and Curie to Congres 

 International de Physique, 1900, tome iii. 



X C. R. exxx. p. 1126. 



§ Ibid. exxx. p. 647. 



ii See Heaviside, ' Electrician/ April 4, 1902. 



% Gbtt. Nach. ii. 1901. 



Y2 



