Abstract
The problem of the impulsive addition of momentum to a simple current system, discussed previously by Rossby and Cahn, is reexamined and the basic equations are solved by a numerical-graphical technique. The equations representing the transient phase are considered first from a linear and then from a non-linear point of view and the differences indicated. The conclusion is reached that the non-linear solution can yield a gravity wave which steepens with time and which propagates normal to the orientation of the initial current. A possible application of the theory to the atmosphere is suggested, in the production of eastward moving pressure-jump lines by southerly currents.