  This note examines the geometry behind the Hamiltonian structure of
isomonodromy deformations of connections on vector bundles over Riemann
surfaces. The main point is that one should think of an open set of the moduli
of pairs $(V,\nabla)$ of vector bundles and connections as being obtained by
"twists" supported over points of a fixed vector bundle $V_0$ with a fixed
connection $\nabla_0$; this gives two deformations, one, isomonodromic, of
$(V,\nabla)$, and another induced from the isomonodromic deformation of
$(V_0,\nabla_0)$. The difference between the two will be Hamiltonian.
