  A formulation of linearized gravity which is manifestly invariant under
electric-magnetic duality rotations in the internal space of the metric and its
dual, and which contains both metrics as basic variables (rather than the
corresponding prepotentials), is derived. In this bimetric formulation, the
variables have a more immediate geometrical significance, but the action is
non-local in space, contrary to what occurs in the prepotential formulation.
More specifically, one finds that: (i) the kinetic term is non-local in space
(but local in time); (ii) the Hamiltonian is local in space and in time; (iii)
the variables are subject to two Hamiltonian constraints, one for each metric.
