  Equation of motion for the galactic tide is treated for the case of a comet
situated in the Oort cloud of comets. We take into account that galactic
potential and mass density depend on a distance from the galactic equator and
on a distance from the rotational axis of the Galaxy. Secular evolution of
orbital elements is presented. New terms generated by the Sun's oscillation
about the galactic plane are considered. The inclusion of the new terms into
the equation of motion of the comet leads to orbital evolution which may be
significantly different from the conventional approach. The usage of the
secular time derivatives is limited to the cases when orbital period of the
comet is much less than i) the period of oscillations of the Sun around the
galactic equator, and, ii) the orbital period of the motion of the Sun around
the galactic center.
