The Terminal Velocity of Fall of Small Spheres in Air

Abstract

AT the recent Winnipeg meeting of the British Association we presented some results on the terminal velocity of fall of approximately spherical spores, which were not in agreement with Stokes's formula (see NATURE, October 14, p. 472). We have succeeded since in making minute spheres of paraffin wax, a certain black wax, and mercury, and have determined their terminal velocities over a wide range of sizes by the same method as in the preceding investigation. The velocities obtained for these spheres are in close agreement with Stokes's formula. The reason for the deviations in the former cases is not clear.