  We present a Hamiltonian formulation of the Schwinger model on the circle in
Coulomb gauge as a semi-bounded self-adjoint operator which is invariant under
the modular group ${\cal M}=\Z$ of large gauge transformations. There is a
nontrivial action of $\cm$ on fermionic Fock space $\mcH_0$ and its vacuum
which plays a role analogous to that of the spectral flow in the formalism
involving the infinite Dirac sea. The formulation allows (i) a description of
the anomaly and its relation to this group action, and (ii) an explicit
identification of the interacting vacuum which arises after the destabilization
of the non-interacting vacuum in $\mcH_0$.
