and Dissociation of Hydrogen Molecules. 



441 



a single electron from the molecule, and are not able to 

 dissociate the molecule into atoms. When the pressure is 

 greater, some of the positive molecules collide with the 

 molecules of the gas before the cathode, and this collision 



5- 



Magnet 



ic Field 



results in a dissociation of the gas into atoms. A positive 

 atom thus formed may attach itself to a neutral molecule 

 and give rise to H 3 . 



The experiments thus confirm for electrons of this speed 

 the conclusion reached by Millikan from his experiments 

 with oil-drops (Phil. Mag. xxi. p. 753 (1911)) that gaseous 

 ionization produced by /3-rays, or by X-rays of all hardnesses, 

 consists in the detachment from a neutral molecule of a 

 single elementary charge. They also verify the theory 

 advanced by J. J. Thomson to account for the results ob- 

 tained in his experiments on positive rays (Phil. Mag. xxiv. 

 p. 234 (1912)), that the electrons and positive rays produce 



