HYPOTHESIS OF RADIANT MATTER 71 



novel phenomenon of the saturation constant; viz., the fact 

 that the flow of electricity through a conducting gas increases 

 proportionately to the voltage between the electrodes up to 

 a maximum, when further increase of potential has practically 

 no effect on the current. This saturation current, it may be 

 remarked, is used to characterize radioactivity; it is admit- 

 tedly a complex phenomenon, and I should be inclined to lay 

 more stress upon the qualitative than the precise quantita- 

 tive results obtained in a number of recent experiments. 



Those who, like Armstrong, oppose the electrolytic dis- 

 sociation hypothesis of Arrhenius, naturally attack the ioni- 

 zation hypothesis with still greater vehemence, and I believe 

 that this will be the battleground of opposing theories for 

 some time to come. As the phenomenon is distinctly a sec- 

 ondary reaction, from our point of view, we need not discuss 

 it in its various aspects, beyond noting that even without 

 detectable radioactive agencies the atmospheric air conducts 

 electricity to a slight extent, varying with location, as well as 

 with the hours of the day. 



The radiations from the active chemical substances present 

 a very complex aspect; besides light and heat, radium and 

 its congeners send out a-, J3-, and 7-rays, respectively elec- 

 tro-positive, electro-negative and neutral when tested in elec- 

 tric and magnetic fields. 



From radium a-rays are sent out about four times as abun- 

 dantly as /3-rays, the 7 variety being relatively few. a-rays 

 are electro-positive, have a speed one tenth of the velocity 

 of light, and a molecular mass of atomic magnitude. They 

 penetrate a few centimeters into air, pass through thin 

 aluminum foil but are stopped by denser metals. As they 

 are but slightly deviable in a magnetic field, their momen- 

 tum is calculated to be enormous; until, however, better evi- 

 dence of the total positive charge which they carry has been 



