( 530 ) 
is proportional to the absolute temperature of the system). *) 
In order to find the condition of equilibrium we have only to 
determine the values of the numbers n, that make the quantity Sor 
log & a maximum. Before we proceed to this investigation we have 
to express the quantity ¢, in the numbers n,. 
Let us suppose that ? is a point of the layer dz, We shall try 
to determine the potential energy for a molecule situated at that 
point. Consider first the contributions from the molecules situated in 
two plane layers at a distance vdz from P. We shall indicate these 
layers by dz, , and dz,4,. We cut from these layers cylindrical rings 
by cireular cylinders having OPO’ as axis and as basis circles with 
OA = ON =r and: OB SOB = r + dr 
as radii. 
The number of the molecules in these elements amounts to 
2 a rdr dz (n,—y + nx»). 
Considering as equal the distance of all these molecules from P and 
representing it by f, we find for their contribution to the potential 
energy of P 
— rde dz (Dos BEP). -  - 7 a eee 
Now we have 
r? + (vdz)* = f? 
and therefore 
EN EE EP 5 
Taking into account (1) and (3) we can replace (2) by 
nde (Drs mep Pf) en ae 
1) Cf my dissertation § 4 p. 15. 
