LIGHT AND THE QUANTUM 117 



advanced the quantum theory which, together 

 with a large number of new experimental ob- 

 servations which followed in its train, indicated 

 the existence of a degree of atomicity in nature 

 far beyond anything yet conceived. Einstein, 

 reviving the corpuscular theory of light, dis- 

 covered a very important law concerning the 

 interaction of light and electrons. Bohr pro- 

 posed the theory that atoms change from one 

 configuration to another per saltum, and thus 

 found a marvelous and unexpected simplicity in 

 the complex science of spectroscopy. 



All this suggests a geometry in which dis- 

 tance is not measured but counted,^ and a kine- 

 matics in which time ceases to have continuous 

 extension, as though the mechanism of a clock 

 were to vanish, leaving only the ticks ! It is hard 

 to predict how far we shall travel in this direc- 

 tion. It is my belief that further discontinuities 

 will be discovered in the physical world, that 

 have not yet been suspected. Nevertheless, it 

 seems likely, on account of the greater general- 

 ity and inclusiveness of the continuum, which I 

 have already mentioned, that we shall return 



1 Dedekind believes that not even Euclidean geometry 

 necessarily implies a continuum. 



