314 On the Adhesion of the Particles 



by no means suppose that the same force will suffice to 

 separate these same particles from each other, when two 

 of them, which are in contact, are drawn in opposite 

 directions along the line passing through their centres. 



The very considerable weight of a drop of water 

 which remains suspended from a solid body shows 

 evidently that this latter force is incomparably greater 

 than I have found the former to be. Now, when a solid 

 body rests on the surface of a liquid, it cannot pene- 

 trate into it without breaking the layer of particles 

 which are at this surface, and which may be considered 

 as forming a sort of pellicle ; in order to break this 

 pellicle, it is evidently necessary to separate the parti- 

 cles which compose it, by compelling them to withdraw 

 from each other directly or nearly in lines passing 

 through their centres, and it is for this reason that small 

 solid bodies specifically heavier than water remain on 

 the surface of this liquid without penetrating into it. 



Likewise, when water issuing from the upper extrem- 

 ity of the shortened capillary tube of an inverted siphon 

 forms a small hemispherical mass, resting on the end of 

 the tube and attached to its walls, the convex surface of 

 this small mass of liquid is formed by a layer of parti- 

 cles which resist, with all the force of their attraction 

 for each other, every effort tending to separate them ; 

 and it is the resistance of this single layer of particles, 

 or of several layers resting immediately one upon an- 

 other, and together forming a sort of very thin pellicle, 

 which sustains the entire weight of the column of water 

 in the other arm of the siphon, which is situated above 

 the level of the surface of this small mass of liquid. 



I have recently established this fact by means of an 

 experiment, which I regard as decisive. 



