OBSERVATION of the flow pattern of a two-dimensional liquid jet directed into a blind cavity formed by solid surfaces indicates that the entire pattern may be treated as a fluidic oscillator circuit. The cavity was in a two-dimensional format, with an end wall transverse to the jet flow and side walls parallel to the jet extending back past the nozzle. The outflow from the cavity was opposite the end wall, remote from the jet nozzle. The two photographic sequences (Figs. 1 and 2) illustrate the flow patterns produced in our two model cavities: the oscillatory nature of the pattern is clear. A schematic diagram of the instantaneous pattern is shown in Fig. 3. © 1969 Nature Publishing Group.