170 THE NEW KNOWLEDGE. 



But owing to the radiation of energy, the velocity is going 

 to diminish, slowly, very slowly, but certainly. There will 

 come a time, then, and a definite time, when this critical 

 velocity will be reached and then, presto ! there will be sud- 

 den convulsion, or explosion, and the rearrangement is ac- 

 complished. 



The potential energy is decreased, the kinetic energy is 

 increased. 



This arrangement must mean the evolution of a large 

 amount *of kinetic energy, and it has been shown that it 

 might easily be sufficient to carry the system out of the 

 atom altogether and we should have, as in the case of ra- 

 dium, a part of the atom shot off with high velocity. 



It is very like the case of a spinning top. The top is 

 stable in a vertical position if the kinetic energy due to its 

 rotation exceeds a certain value. When, however, the veloc- 

 ity diminishes to this critical point, the crash comes and 

 away goes the top, helter-skelter. 



This all agrees with the facts of radio-activity. The 

 radio-activity of radium, for example, is thus an atomic 

 cataclysm. When the point of instability is reached the 

 explosion occurs with the projection of two kinds of particles 

 which are sub-atoms inside the group but free atoms outside. 



One of these is the alpha particle consisting of two or 

 three thousand corpuscles and the other is the atom of the 

 emanation which contains probably about 150,000. The 

 atom of the emanation is of the same type as the atom of 

 radium. Its configuration for steady motion depends on 

 its kinetic energy. Consequently the process is repeated 

 for the emanation, but in a very much shorter time, and we 

 again have the evolution of alpha particles, which seems as 

 a matter of fact to be the atom of helium, together with 

 the formation of another atomic system called emanation X. 



