We study nonlinear waves in polytropic slabs under the joint influence of both self-gravitational and externally imposed gravitational fields. In the long wavelength limit, these obey nonlinear evolution equations akin to the Boussinesq and the KdV equations, with modifications resulting from the effects of self-gravity, or autogravity. We present pole solutions of these equations, including, in particular, a travelling solitary wave. These are surface gravity waves that we call autogravity waves because they are excited by selfgravity.