424 J.LeConte — Apparent Atinirt , '<,„* <n«l I^jnd.^on.^ftr. 



the floating apparatus. Hence, the idea that such a system 

 would take on a horizontal and perpetual motion under the 

 action of molecular forces, is not only inconsistent with funda- 

 mental mechanical principles, but is contradicted by direct ex- 

 periment : for, no motion takes place in such a composite 

 vertical plate, when partly immersed and floating in the liquid.* 

 Moreover, it seems to me, that according to any theory of 

 capillarity which is based upon the action of a tense elastic 

 superficial film, it is clear, that the tensile reaction of the 

 bounding film, which envelops such a floating composite plate, 

 must necessarily be exactly the same in all parts of its perim- 

 eter; so that, it is impossible for the forces due to capillary 

 actions, to disturb the equilibrium of such a body while float- 

 ing in the liquid, so long as its 'component plates are main- 

 tained at a fixed distance apart. It is obvious, that the tensile 

 reaction can only tend to press the plates together ; it cannot 

 produce a motion of translation. It is almost needless to add 

 that in the case.- pre\ i<>u-l\ considered where the ll 



e separated and movabh 



3, the conditions of equilibrium 



e disturbed by the modil 





3s due to their proximit 



y ; and these conditions of equi- 



ium could onlv be realize 



ne! by mutual contact, or by reces- 



i beyond the reach of disl 





t is; likewise, evident, th 



at in cases 1 and 2 the interfering 



modified united boundi 





10 a minimum perimeter 



. which is only secured when the 



bodies are brou-ht in 



contact,. In the composite plate 



above considered, this conditio,, is instantly realized upon par- 



praetieally so much more diflicult to experimentally verify 

 case 3, than cases 1 and 2. For in case 3 when the lloating 

 bodies are brought so near to one another that the in 

 meniscuses form a common enveloping film, the principle of 

 minimum bounding perimeter prevails, and. the verification ot 

 apparent repulsion lai'ls ; for the two bodies are drawn together 



as "in cases \ and ± Tin la< t that hi ^ ease,, lloating bo.li.- 



apparently repel one another at a certain distance, but on 



and re bylVi ive theories 



of capillarity, and was experimental! v verified bv the Abbe" 

 Haiiv and others. 



