SURFACES OF DISCONTINUITY 



635 



were in the range for which pc{t, m) is greater than the right- 

 hand side of the above equation, the film would form, tending to 

 get into the lens shape at first and then, as its growth drew on 

 the adjacent masses A and B for material and modified the 

 potentials so as to restore the condition given by equation [571], 

 would spread out in the film again. If, as in (2) of previous 

 paragraphs, the phases are in such a condition of temperature 

 and potentials that cab < oac + obc, we can show that a mass 



Fig. 5 



of C will not tend to form on the surface between A and B, 

 curved as before to the radius given above, even when p c(^ m) 

 is greater than the critical value on the right hand of [571]. 

 This requires a repetition of the proof on pages 260, 261 with the 

 surface DEIFG in Figure 10 of Gibbs regarded as curved and 

 not plane ; the adaptation of it to this wider geometrical con- 

 dition is given on page 263 (see Fig. 5). The area represented 

 by EH'F is Sac, by EH"F Sbc, by EIF Sab. Va is the volume 

 represented by EIFH', Vb by EIFH", and Vc is the sum of these. 



