Prof. Thomson, On the positive electrification of a rays, etc. 49 



On the positive electrification of a rays, and the emission of 

 Slowly moving cathode rays by radio-active substances. By J. J. 

 Thomson, MA, F.R.S. 



[Bead 14 November 1904.] 



The experiments described below were undertaken with the 

 object of detecting the positive charge on the a rays. Rutherford 



o-£ 



Fig. 1. 



has shown that the a rays are deflected by electric and magnetic 

 forces in the same direction as a positively electrified body, but I 



VOL. XIII. pt. i. 4 



