LXXXII.Bubbles, drops, and Stokes' law. (Paper 2)

Summary In a previous paper by one of the authors it was shown that spherical drops or bubbles surrounded by a more viscous fluid might have a terminal velocity as great as one and a half times that of a solid sphere of equal size and mass. The present paper shows experimentally and theoretically that the surface-tension of the surface of the drop or bubble decreases the terminal velocity. For any radii appreciably less than a certain critical value the drop or bubble behaves almost like a rigid sphere. After a fairly rapid transition, for all radii appreciably larger than the critical the effect of surface-tension is small. Experiments on the terminal velocity for air in water-glass, air in syrup, mercury in syrup, and water in castor-oil, all give critical radii of the order predicted; but the different media show appreciably mutual disagreement, the cause of which is not vet certain.