“…Indeed we know by now that these waves show instabilities at all amplitudes, unless damped by viscosity (Mied, 1976;Klostermeyer, 1982Klostermeyer, , 1983Klostermeyer, , 1991Lombard and Riley, 1996a;Sonmor and Klaassen, 1997). As shown by Lombard and Riley (1996a) it is neither the wave-related shear nor the corresponding stratification which are solely responsible for the growth of linear NMs, but a mixture of the two.…”