CONDUCTION THROUGH GASES 155 



into simpler bodies, as we shall presently see, 

 is the universally accepted explanation of the 

 phenomena of radio-activity. 



Having now dealt with the phenomena of 

 cathode rays and the theoretical results which 

 have followed their discovery, we must turn to 

 the corresponding positive rays, which are emitted 

 from the anode of an exhausted tube through 

 which an electric discharge is passed. If holes 

 be bored in a cathode placed opposite an anode, 

 positive rays will be found to have passed through 

 the holes into the space behind the cathode. They 

 may, if necessary, be sent through a window of 

 thin aluminium foil, and thus examined outside 

 the discharge tube. 



The magnetic and electric deflections of these 

 anode rays are much less marked than the deflec- 

 tions of cathode rays, and stronger fields must be 

 used to examine them. The results show that 

 they are positively electrified particles, with masses 

 corresponding to those of known chemical atoms, 

 instead of the sub-atomic electrons of cathode rays. 



It was again Sir J. J. Thomson who first made 

 an extensive investigation of these positive rays. 

 He passed them through both an electric and a 

 magnetic field, so that they fell on a photographic 

 plate in such a way that all projected particles 

 having the same value of mje formed a single line. 



In hydrogen, for instance, the chief line is found 

 in a position which indicates a value for mje of 

 IO"^ the same as for the hydrogen ion in liquid 

 electrolytes. Another line showing a doubled value 

 for mje indicates a hydrogen molecule carrying a 

 single charge. In oxygen, atoms appeared carry- 



