Robe's restricted three-body problem is reanalyzed with a view to inco
rporate a new assumption, namely that the configuration of the fluid b
ody is that described by an hydrostatic equilibrium figure (Roche's el
lipsoid). In the concomitant gravitational field a full treatment of t
he buoyancy force is given. The pertinent equations of motion are deri
ved, the linear stability of the equilibrium solution is studied and t
he connection between the effect of the buoyancy forces and a perturba
tion of the Coriolis force is pointed out.