  We built three models for the gravitational field of the Galactic bar. These
models are an inhomogeneous ellipsoid, an inhomogeneous prolate spheroid, and a
superposition of four inhomogeneous ellipsoids. Among the three models, the
superposition provides our best approximation to the observed boxy mass
distribution of the Galactic bar. Adding the bar component to an axisymmetric
Galactic model, we have calculated stellar midplane orbits and orbits of some
globular clusters with known kinematical data. For all models we find a secular
dispersion effect upon the orbital energy and angular momentum, as measured in
the Galactic inertial frame. This effect might be relevant to explain the
orbital prograde-retrograde distribution of globular clusters. For the stellar
kinematics, we study the connection between the sense of orbital motion in the
midplane and the onset of chaos in the presence of the bar. In the inner region
of the bar, chaos is induced by an axisymmetric central component (bulge) and
it arises in orbits that change its orbital sense from prograde to retrograde
and vice versa as seen from an inertial reference frame. Outside the bar
region, chaos appears only in prograde orbits. Our results concerning such
connection are consistent and extend those obtained for midplane orbits in the
presence of only a spiral pattern in the axisymmetric Galactic model.
