  Fay's trisecant formula shows that the Kummer variety of the Jacobian of a
smooth projective curve has a four dimensional family of trisecant lines. We
study when these lines intersect the theta divisor of the Jacobian, and prove
that the Gauss map of the theta divisor is constant on these points of
intersection, when defined. We investigate the relation between the Gauss map
and multisecant planes of the Kummer variety as well.
