ABSTRACT
One is familiar with the ways in which small amounts of liquid on a solid surface behave, not only from laboratory studies but also from everyday observations made of our immediate surroundings. One knows that drops of water on an inclined solid surface can remain stationary or can move under gravity. If a waxed paper is withdrawn from water, the thin sheet of water formed initially will break up into beads. On the other hand, if the waxed paper is withdrawn from oil, the sheet of oil formed will drain and grow thinner, but will not form beads. Leaving aside the effects of gravity, two types of behavior are observed on a given solid surface, one where the liquid forms beads and the other where it forms a film. It is easy to assume that liquids which have strong affinities for a solid will form films such that the liquid-solid contact is maximized, while those that have weaker affinities will collect themselves into beads.
