878 Mr. Wilson Taylor on the Coalescence oj 



down to microscopic dimensions, nor how closely they ap- 

 proached each other so long as they did not touch. But when 

 contact was made a powerful force instantly came into play 

 that caused the two masses to coalesce and become one sphere. 

 This was found to be the case with all liquids, independently 

 of the relative sizes of the spheres, and at all temperatures of 

 the liquids. With mercury the action was instantaneous and 

 very powerful. Sometimes, however, two or more mercury 

 spheres would apparently lie in contact without coalescing, 

 but on examination with the microscope there was always 

 found some foreign substance which had accumulated on 

 their surfaces that prevented their coming into contact. 

 The question arose : Is it not possible that the same 

 enveloping force which causes visible spheres to coalesce 

 also causes the free molecules of a gas to aggregate them- 

 selves into a liquid ? 



Now, in any self-contained system of material masses any 

 change in energy is from potential energy, either directly or 

 through kinetic energy of large masses, into kinetic energy 

 of the molecules of the system, that is,, into heat. For to 

 produce any change the forces of the system must become 

 statically unbalanced, so that the resultant force does work 

 against the inertia of large and small masses causing them 

 to acquire kinetic energy. 



Tt has long been observed that in many respects surface- 

 tension appears to act as though it were something of the 

 nature of an elastic envelope about a liquid mass trying to 

 compress the mass into a smaller volume by contracting the 

 area of the envelope. This tendency to change the volume, 

 however, is due solely to the curvature of the enveloping 

 surface, which tends to cause compression on the concave 

 side and expansion of volume on the convex side. If there 

 is no curvature there is no tendency either way to alter the 

 volume. The fundamental nature of the tension, then, is to 

 tend to decrease the area of the surface. 



Let us consider, then, a system of three spheres of 

 water whose diameters are '3, *4, and '5 cm. The potential 

 surface energy of the system is Tx7r{(*3) 2 + ('4) 2 + (*5) 2 }, or 

 •5O77-T ergs. If these spheres be brought into contact, they 

 will coalesce into one sphere whose diameter is *6 cm., and 

 whose potential surface energy is Tx7r( # 6) 2 , or '367rT ergs. 

 The potential surface energy which has been transformed 

 into heat by coalescence is, therefore, '147rT ergs. If we 

 take, according to the best available data, T=733 dynes 

 per cm. at 15° C., this energy amounts to 7*71 X 10" 7 calorie, 

 where J = 4*184 X 10 7 . 



