82 SCIENCE AND IMMORTALITY 



showing how corpuscles must group themselves 

 in different atoms,* and have proved that the 

 corpuscles in the atom probably revolve in their 

 orbits, either in concentric rings or in concentric 

 shells. In the same way it has been shown that 

 the relationship between atomic weight and other 

 atomic characters is a dynamical necessity, and also 

 that the abstraction of a single corpuscle may 

 break down the whole atom. 



The illustration of the floating needles, however, 

 is not quite correct, since the equilibrium of the 

 atomic corpuscles depends largely on their velocity, 

 even as the equilibrium of a top depends on the 

 rate at which it is spinning. On this more com- 

 plex conception, we may think of an atom as a 

 sphere of positive electricity, enclosing a number of 

 negatively electrified corpuscles, maintained in a 

 condition of equilibrium by forces of attraction, 

 and repulsion, and kinetic energy ; and a radio- 

 active substance may be defined as one wherein 

 the velocity of the constituent particles of its 

 atoms has fallen so low that equilibrium has been 

 destroyed, and disruption and rearrangement of 

 the corpuscles is in process. In the case of every 

 atom, the velocity of the atomic corpuscles must 

 decrease as energy is radiated away, and ultimately 

 a time must come when every atom will break up 

 and show the phenomenon of radio-activity. But 



