  A direct link between the topological complexity of ferromagnetic media and
their dynamics has recently been established through the construction of
unambiguous conservation laws as moments of a topological vorticity. In the
present paper we carry out this program under completely realistic conditions,
with due account of the long-range magnetostatic field and related boundary
effects. In particular, we derive unambiguous expressions for the linear and
angular momentum in a ferromagnetic film which are then used to study the
dynamics of magnetic bubbles under the influence of an applied magnetic-field
gradient. The semi-empirical golden rule of bubble dynamics is verified in its
gross features but not in its finer details. A byproduct of our analysis is a
set of virial theorems generalizing Derrick's scaling relation as well as a
detailed recalculation of the fundamental magnetic bubble.
