Extensions on the foundations of the mechanics of fluids. Basic concepts will be emphasized; transition from incompressible and potential flow to weakly compressible flow; acoustics and sound generation; transonic flow; fully compressible flow; flow past bodies and shock waves; small-Mach number expansion; Navier-Stokes shock structure; elements of the kinetic theory of gases; Lagrangian form of equations of motion; velocity-gradient tensor and vorticity; vortex dynamics; exact solutions; incompressible potential flow; free-streamline flows; scalar mixing.