PROBLEMS OF MODERN SCIENCE 



menon, the theory of light, and in fact the whole 

 of Physics thus became virtually a branch of 

 mechanics, and so it always will be so long as 

 we are dealing with what I have called macroscopic 

 phenomena, or the phenomena relating to matter 

 in bulk. 



But we have no obvious justification for the 

 assumption that the laws we perceive in matter 

 in bulk are in any way even in close resemblance 

 to those which describe the behaviour of the 

 ultimate indivisible unit of matter, and still more 

 those which are applicable to the separate com- 

 ponent parts actually inside that indivisible unit. 

 This unit is, of course, the atom, and the com- 

 ponent parts are the positive and negative electrons. 

 An electron is not matter, but special groups 

 forming atoms constitute matter. Now there are 

 many wide branches of Physics in which the 

 existing phenomena shewn by matter are not, as 

 in ordinary mechanics, shewn by it as a bulk, but 

 are shewn by the individual units acting quite 

 independently of one another. Of such is the 

 radiation given out by a body, whether under the 

 influence of heat or any other agency. And it is 

 precisely in such regions that the classical electro- 

 dynamics is not only unable to offer explanations of 

 phenomena, but can be shewn to be incompatible 

 with such phenomena if we assume it valid in the 

 microscopic field presented by an atom and its con- 



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