Persistent superfluid flow.

In a recent communication to Physical Review Letters (33, 1073; 1974), Galkicwicz and Hallock report the first really satisfying demonstration of a persistent superfluid current in a helium film. In their experiment, which was carried out at the Amherst campus of the University of Massachusetts, they started the 4He film moving at a velocity of about 5 cm/s around a closed path some 40 cm in length, and were then able to show that the energy of flow did not measurably diminish over a period of several hours