  The Hamiltonian theory of isomonodromy equations for meromorphic connections
with irregular singularities on algebraic curves is constructed. An explicit
formula for the symplectic structure on the space of monodromy and Stokes
matrices is obtained. The Whitham equations for the isomonodromy equations are
derived. It is shown that they provide a flat connection on the space of the
spectral curves of the Hitchin systems.
