where M denotes a constant; so that [psi] is an elliptic integral of
the second kind.
The quiescent ellipsoidal surface, over which the motion is entirely
tangential, is the one for which
d[psi]
2(a² + [lambda])--------- + [psi] = 0, (19)
d[lambda]
and this is the infinite boundary ellipsoid if we make the upper limit
[lambda]1 = [oo].