  When the mass of one of the two bodies tends to zero, Weyl's definition of
the gravitational force in an axially symmetric, static two-body solution can
be given an invariant formulation in terms of a force four-vector. The norm of
this force is calculated for Bach's two-body solution, that is known to be in
one-to-one correspondence with Schwarzschild's original solution when one of
the two masses l, l' is made to vanish. In the limit when, say, l' goes to
zero, the norm of the force divided by l' and calculated at the position of the
vanishing mass is found to coincide with the norm of the acceleration of a test
body kept at rest in Schwarzschild's field. Both norms happen thus to grow
without limit when the test body (respectively the vanishing mass l') is kept
at rest in a position closer and closer to Schwarzschild's two-surface.
