( 584 ) 
Dae ' ; 
This equation runs S=F{ } in which S represents the entropy, u 
5 
the energy, » the frequency of the free vibrations of the vibrator and F'a 
é 
in which ¢ represents a small quantum of energy, into which the 
total energy of all vibrators with frequency pv is divided, after which 
these atoms of energy are distributed over the different vibrators accord- 
ing to the laws of probability. If these equations are to be in 
harmony, « must really be = Ar, as PLANcK assumes. The question, 
however, is, whether there is sufficient cause to assume that these 
still unknown function. The other equation!) may be written S=F' be 
equations do harmonise. And in my opinion this is not the case. 
For the first equation holds for real bodies, the second for the 
fictitious systems of vibrators, which most likely do not occur in 
the real bodies. In the first place so many different kinds of vibrators 
with so many different free periods are hardly to be assumed. 
And moreover every vibrator will, no doubt contain a moving electron 
whose motion strictly speaking is controlled not by a differential, 
but by an integral equation, so that the vibrator has not one, but 
a whole series of periods for its free vibrations. 
Now PrarckK asserts that it is of no importance whether his radiating 
systems agree with those really occurring in nature. For, he says’), 
Kircuyorr’s law teaches that we always get the same normal 
spectrum independent of the nature of the walls. This, however, 
seems to me an inaccurate interpretation of the law of KircHHorr. 
For this law states only something about walls occurring in nature, but it 
does not decide anything about the spectrum that would be formed 
in a space inclosed by walls with fictitious properties which deviate 
from what really occurs in nature. Hence the interpretation of 
Krecunorr’s law that the spectrum would be independent of the 
nature of the walls, is to be rejected. The real gist of the law is 
much better rendered by saying that all walls occurring in nature 
have such properties that they give rise to the same spectrum ; 
what these properties are which all real walls have in common, is 
not yet quite known. Only on special suppositions did Lorentz *) 
succeed in examining this. 
That this acceptation of KircuHorr’s law is really the correct one 
appears from this that in his cited paper Lorentz succeeded in 
imagining walls of such a nature that the thermodynamic laws of 
radiation are not fulfilled in their mutual radiation. He imagined, 
1) loc. cit. p. 153 in the middle. 
2) loc. cit. p. 100 and 101. 
35) H. A. Lorentz, These Proc. IX p. 436, 1900. 
