CONFLICT WITH WAVE-THEORY 187 



amount in the box reaches a whole quantum, it enters 

 the atom. In the second the atom uses the small frac- 

 tion of a quantum offered to it to buy a ticket in a 

 sweepstake in which the prizes are whole quanta; some 

 of the atoms will win whole quanta which they can 

 absorb, and it is these winning atoms in our retina 

 which tell us of the existence of Sirius. 



The collection-box explanation is not tenable. As 

 Jeans once said, not only does the quantum theory 

 forbid us to kill two birds with one stone; it will not 

 even let us kill one bird with two stones. I cannot go 

 fully into the reasons against this theory, but may 

 illustrate one or two of the difficulties. One serious 

 difficulty would arise from the half-filled collection- 

 boxes. We shall see this more easily if, instead of 

 atoms, we consider molecules which also absorb only 

 full quanta. A molecule might begin to collect the 

 various kinds of light which it can absorb, but before it 

 has collected a quantum of any one kind it takes part 

 in a chemical reaction. New compounds are formed 

 which no longer absorb the old kinds of light; they have 

 entirely different absorption spectra. They would have 

 to start afresh to collect the corresponding kinds of 

 light. What is to be done with the old accumulations 

 now useless, since they can never be completed? One 

 thing is certain; they are not tipped out into the aether 

 when the chemical change occurs. 



A phenomenon which seems directly opposed to any 

 kind of collection-box explanation is the photoelectric 

 effect. When light shines on metallic films of sodium, 

 potassium, rubidium, etc., free electrons are discharged 

 from the film. They fly away at high speed, and it is 

 possible to measure experimentally their speed or 

 energy. Undoubtedly it is the incident light which 



