“…In the same paper (Marussi 1979) it has also been shown that if a steady rotation is superposed to the residual field, the resulting potential W will be written as in which wl, w 2 , w 3 are the components of the rotation vector along the x-,yand z-axes respectively, w2 = w: + 0; + w:, and R the distance of a point P(x, y, z) from the rotation axis drawn through the centre of mass Po. The equipotential surfaces W again constitute a family of concentric homothetic quadrics, under circumstances hyperboloids or ellipsoids, which might degenerate into hyperbolic or elliptical cylinders, or even into a family of parallel planes.…”