2o POPULAR SCIENCE MONTHLY. 



Since the energy emitted from the radio-elements is for the most 

 part kinetic in form, it is necessary to suppose that the a and /? 

 particles were originally in rapid motion in the atoms from which 

 they are projected. The disintegration theory supposes that it is the 

 atoms and not the molecules which break up. Such a view is neces- 

 sary to explain the independence of the rate of disintegration of radio- 

 active matter, of wide variations of temperature, and of the action 

 of chemical and physical agents at our command. This must be 

 conceded if the term atom is used in the ordinary chemical sense. It 

 is, however, probable that the atoms of the radio-elements are in 

 reality complex aggregates of known or unknown kinds of matter, 

 which break up spontaneously. This aggregate behaves like an atom 

 and can not be resolved into simpler forms by external chemical or 

 physical agencies. It breaks up, however, spontaneously with an evolu- 

 tion of energy enormous compared with that released in ordinary 

 chemical changes. This question will be considered later. 



The disintegration theory assumes that a small fraction of the 

 atoms break up in unit time, but no definite explanation is, as yet, 

 forthcoming of the causes which lead to this explosive disruption of 

 the atom. The experimental results are equally in agreement with 

 the view that each atom contains within itself the potentiality of its 

 final disruption, or with the view that the disintegration is precipitated 

 by the action of some external cause, that may lead to the disintegration 

 of the atom, in the same way that a detonator is necessary to start 

 certain explosions. The energy set free is, however, not derived from 

 the detonator, but from the substance on which it acts. There is 

 another general view which may possibly lead to an explanation of 

 atomic disruption. If the atom is supposed to consist of electrons or 

 charged bodies in rapid motion, it tends to radiate energy in the 

 form of electromagnetic waves. If an atom is to be permanently 

 stable, the parts of the atom must be so arranged that there is no loss 

 of energy by electromagnetic radiation. J. J. Thomson has in- 

 vestigated certain possible arrangements of electrons in an atom which 

 radiate energy extremely slowly, but which ultimately must break up 

 in consequence of the loss of internal energy. According to present 

 views, it is not such a matter of surprise that atoms do break up 

 as that atoms are so stable as they appear to be. This question of 

 the causes of disintegration is fundamental and no adequate explana- 

 tion has yet been put forward. 



Radioactive Products. 



Rutherford and Soddy showed that the radioactivity was always 

 accompanied by the appearance of new types of active matter which 

 possessed physical and chemical properties distinct from the parent 



