( 325 ) 
e 
n= { Fog ()dw where: HE EA 
en 
Possibly this p is nothing but the energy per unity of volume, 
which quantity we are most inclined to call “density of radiation.” 
For the distribution of the magnetic forces the entropy will consist 
of another term formed in a similar way. Possibly however we 
shall have to find the entropy not from the electric and the magnetic 
forces separately, but from the vectors of POYNTING. 
We find therefore the analogue of matter at the absolute 0-point 
not in a space without radiation, but in absolutely regular movement, 
e.g. in a plain wave of monochromatic light, everywhere with the 
same amplitude. Let us represent this wave by: 
2 
hf cos. = (t— 2) 
Here we must take into consideration, that in this case f, and fs 
are not independent of each other, so that we cannot simply add 
the entropy for these two terms. Probably we have to diminish the 
amplitude everywhere with: 
2 
So cos. wy and fp sin. wilds 
A 
and we have to take for # the chance that the remaining amplitude 
lies between certain limits, i.e. 
jie 9 
f= —e where c=0 and f') =f, — fy cos. — 
: CY 1 1 1 0 ‘ à 
This is analogous to the way, in which we prove for a gas of 
O°, which moves as a whole, that the quantity H of BOLTZMANN 
becomes oo. 
If we put for p the mean energy, we find: 
Pets hen oe 
n={¥ fe fit ee ive Pinte AR 2 df = 
c 
~~ 
So the entropy is — o, 
