52 Mr. J. LeConte on the Apparent Attractions 



be properly or safely invoked to explain these phenomena 

 without the restrictions imposed by the introduction of the 

 negative and positive molecular pressures, which constitute 

 such important factors in the physico-mathematical analyses 

 of these questions. 



Proposed General Explanation. 



In the following explanation of the " apparent attractions 

 and repulsions of small floating bodies/' I have referred this 

 class of phenomena to two fundamental principles of capil- 

 larity which are abundantly verified by observation and expe- 

 riment, viz.: 1st, that in every case, whether of moistened or 

 non -moistened bodies, there exists an adhesion between the 

 solid and the liquid; and 2nd, that the capillary forces are, in 

 any given case, inversely proportional to the radii of curva- 

 ture of the meniscuses, and their resultants are directed toward 

 the centres of concavity. It seems to me that these two fun- 

 damental and well-established principles of capillary action 

 will explain the whole class of phenomena in a much more 

 consistent and satisfactory manner. 



Case 1. Fig. 1. Before the two bodies are brought near each 

 other, the concave meniscus around each of them having the 

 same radius of curvature on all sides, each of the floating- 

 bodies is in equilibrium under its action. But when brought 

 so near that their meniscuses join each other, the radius of cur- 

 vature of the united intervening concave meniscus at m 

 (fig. 1) is less than that of the exterior concave meniscuses at 

 a and b, and its superior tension acts upon both bodies toward 

 a common centre of concavity at 5. Hence, by virtue of the 

 smaller radius of curvature of the intervening tense film, the 

 interior forces prevail, and the two bodies are drawn together. 



Case 2. Fig. 2. The same explanation applies to this case. 

 The common or united intervening convex meniscus being 

 attached to the bodies at e and g (fig. 2), has a smaller radius 

 of curvature than the exterior convex meniscuses at d and/. 

 Hence in this case likewise, by virtue of the smaller radius of 

 curvature of the intervening contractile elastic film, the inte- 

 rior forces necessarily prevail, and the two bodies are drawn 

 together. 



Case 3. In this case (fig. 3) it is evident that as the centres 

 of concavity of the interfering meniscuses are in opposite 

 directions, the common or united meniscus formed by their 

 union, as kn, must have a radius of curvature greater than 

 that of either of the exterior meniscuses at c and o f . Hence, 

 by virtue of the smaller radius of curvature of the exterior 

 tense elastic films at c and o', the exterior capillary forces must 



