430 Dr. G. Bakker on the 
value as for the point C 5 . The reciprocal value o£ the 
density of the drop is given by the abscissa of A 5 . A con*- 
formable consideration we may make for each pair of points 
below the part HK of the empiric isotherm. If, for instance, 
in the points A 2 and C 2 the thermodynamic potential has the 
same value, these points determine the state of a spherical 
bubble of vapour and of the liquid which surrounds the birbble. 
In the same manner we have found above, that a pair of points 
above the part HK of the empiric isotherm determine the state 
of a spherical drop of liquid with its vapour. 
A part of the theoretical isotherm that we, however, have 
not considered hitherto is the part AjP (fig. 7). This part 
of the isotherm corresponds, as everyone knows, with the 
phases, which cannot be realized under uniform pressure, 
because the pressure would be increased with the increase of 
the volume. Therefore Maxwell says in his text-book i Theory 
of Heat': " We cannot, therefore, expect any experimental 
evidence of the existence of this part of the curve, unless, as 
Prof. J. Thomson suggests, this state of things may exist in 
some part of the thin superficial stratum of transition from a 
liquid to its ovm gas, in which the phenomena of capillarity take 
place." 
Now the curve AEC in fig. 5 presents the relation between 
half the sum of the maximum and minimum value of the 
pressure \ „» = P f ^ n every point of the capillary layer 
and the reciprocal value of the density in this point, and, as 
I have demonstrated above, the point E on the curve AEC, 
where the ordinate has its minimum value, and where the 
thermodynamical potential has the same value as in the 
homogeneous phases of the liquid and the vapour (the cor- 
responding points are A and 0) lies exactly on the theoretical 
isotherm. Therefore we have the following theorem: 
Every pair of points of the isotherm, for which the thermo- 
dynamical potential has the same value (fig. 8) (as A 8 and C <s , 
A 7 and C 7 &c), corresponds above the rectilinear part HK of 
the empiric isotherm to a spherical drop of liquid, such, that 
the state in the interior of the drop and the state of the vapour, 
which surrounds it, is determined hi a singular manner by the 
situation of this pair of points. In the same manner, every 
pjair of points below the rectilinear part HK of the empiric 
isotherm (A 3 and C 3 , A 2 and 2 , &c), for which the thermo- 
dynamical potential has the same value, corresponds to a 
spherical bubble of vapour. If ice note construct the curves, 
such as A 6 JB 6 C G , A 3 B 3 C 3? &c, which present the relation between 
