wien: recent theories of heat and radiation 275 



of energy for the general formula of the theory of quanta, but then 

 our need for adequate causes remains unsatisfied, and, besides, we 

 can not in this way avoid being forced to use the theory of quanta 

 in connection with the classical theory of mechanics and electro- 

 dynamics. So long as these relations remain unknown, the 

 theory will stand on uncertain ground. At the moment, the best 

 way appears to be to apply the theory of quanta to as large a 

 number as possible of the problems related to the theory of heat. 



We may begin with the theory of radiation in the form given 

 by Debye in connection with the theory of Rayleigh and Jeans. 

 And this has the additional advantage of bringing out more clearly 

 the true meaning of the theory of quanta, namely, that another 

 partition of energy takes place, for the energy can only be divided 

 in parts of magnitude hv.- This theory of quanta also lies at 

 the foundation of the theory of specific heat, for the heat of solids 

 is identified with the vibrations of the atom. 



The assumption that energy can only be distributed in mul- 

 tiples of hv corresponds with the first hypothesis of Planck, that 

 emission and absorption can only take place in aliquot parts of 

 magnitude hv. But it is well known that this theory is open to 

 serious objections, for a discontinuous absorption of continuous 

 radiation is hardly imaginable. Therefore Planck has now given 

 up the assumption of quanta for the absorption and applies the 

 hypothesis only to the phenomenon of emission, leaving the ab- 

 sorbed energy to reach any arbitrary value. The question then 

 arises, How is it possible to bring this into harmony with the 

 theory of specific heat? 



According to Planck's new theory, each atom conceals a quan- 

 tity of energy the mean value of which is ^ for each free vibration. 



This energy exceeds the heat energy, even at temperatures which 

 are not very low. Is it therefore possible to assume two kinds of 

 energy of vibrations, one that can not be transferred and another 

 that we call the energy of heat? If elastic vibrations remain in 

 the solid in such an amount that the he^t energy is only a small 



- Where v is the number of vibrations, and /( a universal constant. 



