Soap Bubbles
and the Forces which Mould Them

4o SOAP-BUBBLES, AND time ago is still resting against the water-skin. The buoyancy of the glass bulb is trying to push it through, but the upward force is just not sufficient. I will however pour a few drops of ether into a glass, and simply pour the vapour upon the surface of the water (not a drop of liquid is passing over), and almost immediately sufficient ether has condensed upon the water to reduce the strength of the skin to such an extent that the frame jumps up out of the water. There is a well-known case in which the difference between the strength of the skins of two liquids may be either a source of vexation or, if we know how to make use of it, an advantage. If you spill grease on your coat you can take it out very well with benzine. Now if you apply benzine to the grease, and then apply fresh benzine to that already there, you have this result—there is then greasy benzine on the coat to which you apply fresh benzine. It so happens that greasy benzine has a stronger skin than pure benzine. The greasy benzine therefore plays at tug-of-war with pure benzine, and being stronger wins and runs away in all directions, and the more you