This device has a stirrer rotated by a handle to demonstrate the flattening of a sphere of oil rotating in a mixture of water and alcohol. Oil is deposited along a vertical axis in the tank. The oil takes on a spherical form. If the oil and the water-alcohol mixture have the same density the oil sphere freely floats. If one revolves the axis slowly (one turn every 5 seconds) the oil sphere begins to flatten at the "poles". A maximum of this flattening occurs at 3 to 4 turns per second. If the angular velocity is still larger the oil takes the form of a torus, loose from the axis. At even higher velocities the torus breaks up into small spheres which rotate around their own axis.
Max Kohl, Chemnitz, Νο52,659