16 ROYAL SOCIETY OF CANADA 



products which obviously emit a rays. In the rayless product, the 

 a particle is expelled with a velocity less than 1.5 X 10^ cms. per 

 second, and so fails to produce much electrical effect. 



These considerations have an important bearing on the question of 

 whether matter in general is radioactive. The property of emitting a 

 rays above the minimum velocity required to produce ionization in the 

 gas may well be a property only of a special class of substances and 

 need not be exhibited by matter in general. At the same time, the 

 results suggest that ordinary matter may be undergoing transformation 

 accompanied by the expulsion of a particles at a rate much greater 

 than uranium without producing appreciable electrical or photographic 

 action. 



McGill University, Montreal. 

 May 8, 1905. 



