ELECTRONS AND ATOMS 41 



active decomposition. The Daltonian atom is 

 thus only stable and indivisible within certain 

 limits of experimentation. 



As the atomic weight of the atom, in 

 Dalton's sense, goes on increasing, its content 

 of energy per unit amount of matter is heaped 

 up, and a limit of atomic stability is reached 

 as the atomic weight increases. This is 

 shown by the fact that uranium and radium, 

 those elements which show spontaneous 

 disruption, are also those with the highest 

 atomic weights, as well as by the converse 

 observation, that in those situations where 

 chemical atoms are probably being created 

 by high tension energy, it is those elements 

 with low atomic weights such as hydrogen, 

 and helium, which are present in largest 

 amounts, as shown by stellar spectroscopy. 



It is also a curious fact that there appear 

 to be a series of intervals or levels of stable 

 equilibrium in the building up of the elements, 

 bearing a superficial analogy to musical 

 octaves. With approximately equal additions 

 in the atomic weight, there are recurrences 

 of the same chemical properties in the elements 

 so that the majority of the known elements 

 can be arranged in groups or periods according 

 to what is known as the periodic law. So 

 completely does this law run through the 



