THEORIES OF MATTER 5 



as radium, uranium and thorium. We know that 

 the emanations are powerful, and that they are not 

 of a simple character, for the " radiations " consist 

 of separable emissions. Among these are what are 

 known as the a rays, which consist of particles of 

 matter sent forth with an enormous velocity, highly 

 charged with positive electricity and capable of 

 producing the ionisation of gases. The particles of 

 matter forming these emanations are considered by 

 physicists to differ from the chemical atom and are 

 called primary atoms, corpuscles, electrons and 

 metabolons. Whatever their nature may be, they 

 appear to be similar to the ions dissociated from 

 matter in many ways, and they are charged with 

 such an amount of energy as to be phosphorescent. 

 When solid radium nitrate is brought near to a 

 suitable screen, the latter is seen to be dotted all 

 over with brilliant specks of light (visible through a 

 lens) due to " the bombardment of the screen by 

 the electrons hurled off by the radium." Among 

 the emanations are /3 rays, which also consist of 

 matter projected with a high velocity, charged with 

 negative electricity, and having properties similar 

 to the cathode rays emitted from a vacuum tube. 

 But the emissions from radio-active bodies do not 

 all consist of matter, for there are 7 rays which con- 

 sist of a wave-like motion similar to light, and are 

 probably an exhibition of energy emitted from the 

 material. 



Experiments have shown that radio-active bodies 

 owe their activity to atomic changes in the material, 

 that the atoms of such materials are undergoing 

 disintegration, that in their movements such atoms 



