588 
For molecules with one degree of liberty (harmonically and non- 
harmonically vibrating resonators) the question could be treated 
completely. The result’) that was found can be formulated in the 
terminology of this paper as follows: 
Lor an ensemble of such molecules (resonators) BoLvmMann’s relation 
between entropy and probability will exist then and only then when 
the steady motions are characterised by the condition: 
aT 
— | dgilp = constant numerical values 2,,2,, . . (29) 
v A 
« 
which condition is invariant with respect to adiabatic changes *). 
Prianck’s hypothesis of the energy-steps and Desive’s quantum 
hypothesis for resonators which do not vibrate harmonically fulfil 
this condition £2,, £2,,... being here equal to 0,4,2h,... 
It is however still doubtful whether for molecules with more 
than one degree of liberty the above given necessary and sufficient 
connexion remains valid between the adiabatic hypothesis on one 
hand and BoLrzManN’s relation between entropy and probability on 
the other hand. 
Remarks A. Of late it has become usage to introduce the rela- 
tion between probability and entropy (or free energy). 
Slag We marie ip ea oer es AAE) 
al B log Wed te a Sean en a 
simply as a postulate. 
The problem diseussed in this paragraph might seem to be rendered 
superfluous by this. The author has proved however that the 
question is only removed to another point *). 
B.*) By a reversible adiabatic compression black radiation is 
converted into black radiation whether within the reflecting envelope 
a black grain is present as a katalysator or not. Analogously in a 
gas with molecules without dimensions and on which no forces are 
acting a distribution of velocities according to MaxwerLr. becomes 
one of MaxwerLL whether during the reversible adiabatic compression 
1) Comm. D § 7. 
*) In this theory of radiation PLANCK first leaves the energy-quanta undetermi- 
ned. At a certain moment in order to bring the obtained radiation formula 
im harmony with WieN’s law he ascribes to them the value hy (see PLANCK, 
Vorlesungen über Wärmestrahlung I, Aufl. 1906, p. 153, Gl. 226. Comp, also the 
other quanta hypotheses, Le. § 6). This is the reason why the hypothesis of the 
energy steps is in harmony wilh the second law (and with the adiabatie hypothesis). 
3) 1. e Introduction. 
4) See Communication C § 4. 
