I. On some Transformations in Films when brought in contact with Surfaces of Glass.

(1.) Let a film be formed on the rim of a cylindrical wine-glass, at or very near its margin; cover it immediately with a watch-glass, and holding the latter firmly in its place, invert the whole, so that the film is placed in a vertical position. The film will now attach itself to the watch-glass at the lowest point where it is in contact with the margin of the wine-glass, and will run up the concave surface of the former. At the same time, the film will leave the margin of the wine-glass at its upper edge, and retreat into the glass, running down its inner surface. A film of the form of the segment of a sphere will thus be produced, which, with the upper portions of the inner surfaces of the watch-glass and wine-glass, will form a hollow filled with air, as shown in fig. 1. This state of matters will remain the same, in whatever position we now place the wine-glass, the figure which has thus been produced being one of equilibrium. The phenomenon produced arises from the fact, that when the original film is first taken up on the margin of the wine-glass, a drop of liquid always remains in the bottom of the glass, and when the glass is inverted, so as to bring the film into the vertical position, this drop runs down the inner surface of the glass till, reaching its lowest point, it brings the film into close contact with the watch-glass; the film now attaches itself to and spreads itself over the surface of the latter in a similar way to what takes place when a bubble blown from a pipe is brought into contact with any smooth surface, whilst the original system of equilibrium being now disturbed, the upper part of the film is put in motion, and a new system of equilibrium is formed.