The physical characteristics of a certain class of stable perturbations in an idealized oceanic current regime are investigated theoretically and compared with some observed featur es of the Gulf Stream. The mathematical model envisages an idealized two-layer fluid with a deep lower layer that remains essentially in static balance. T he upper layer, when in equilibrium, is characterized by a region of uniform geostrophically balanced current (hence of nonuniform thickness); adjoining this is a second region of uniform thickness that is at rest....