LIGHT AND THE QUANTUM 121 



however, been entirely abandoned in favor of 

 Maxwell's view that they are periodic disturb- 

 ances in electric and magnetic fields. It is a 

 most remarkable fact that this great revolution 

 in physical thought was accomplished without 

 abandoning a single one of the set of mathe- 

 matical equations derived from the old theory 

 of optics. Does this not suggest that we may 

 have still another revolution in our physical 

 concepts and again retain the whole mathemati- 

 cal theory of optics ? Yet it would seem that any 

 new theory must begin with the assumption of 

 some periodic phenomenon spreading outward 

 in all directions from the emitting source. 



Now comes, however, the revival of the cor- 

 puscular theory of light. I cannot describe here 

 the beautiful experiments which corroborate 

 Einstein's surmise that the energy of radiation 

 consists of quanta or discrete corpuscles. Indeed 

 there seems to be enough experimental evidence 

 to permit us to announce two separate laws for 

 the process of light. They seem to be mutually 

 contradictory, and yet if they are both correct 

 deductions from accurate observation the para- 

 dox must be due to our retaining too tena- 

 ciously some doctrine which has outlived its use- 

 fulness. Our task is therefore to seek some new 



