54 POPULAR LECTURES AND ADDRESSES. 



enlarge the surface of contact would be aided 

 by the molecular forces, so that the liquids, if 

 not kept separate by gravity, would become 

 thoroughly mixed. No instance, however, of 

 a phenomenon of this kind has been discovered, 

 for those liquids which mix of themselves do so 

 by the process of diffusion, which is a molecular 

 motion, and not by the spontaneous puckering 

 and replication of the boundary surface as would 

 be the case if T were negative." 



It seems to me that this view is not correct ; 

 but that on the contrary there is this " puckering " 

 as the very beginning of diffusion. What I have 

 given in the lecture as reported in the text above 

 seems to me the right view of the case as regards 

 diffusion in relation to interfacial tension. 



It may also be remarked that Clerk-Maxwell, 

 in the large print paragraph of p. 59, preceding 

 equation (i), and in his application of the term 

 potential energy to E in the small print, designated 

 by energy what is in reality exhaustion of energy 

 or negative energy ; and the same inadvertence 

 renders the small print paragraph on p. 60 very 



