1199 



Planck is of opinion that the expression [ila) is of' general applica- 

 tion, for high as well as for low temperatures. According to our 

 derivation the more complicated ^) formula (6) would represent the 

 generalij valid relation, which is only transformed to the form {11a) 

 for very low temperatures. 



Christmas 1918. {To he continued). 



^) Also Einstein, Debye and otliers already derived more complicated relations, 

 which are considered to represent the relations better than Planck's simple formula. 



