Surface tension

[Sarah]

That property, due to molecular forces, which exists in thesurface film of all liquids and tends to bring the contained volumeinto a form having the least superficial area. The thickness of thisfilm, amounting to less than a thousandth of a millimeter, isconsidered to equal the radius of the sphere of molecular action,that is, the greatest distance at which there is cohesion between twoparticles. Particles lying below this film, being equally acted onfrom all sides, are in equilibrium as to forces of cohesion, butthose in the film are on the whole attracted inward, and tensionresults.