  The feasibility of an experimental determination of the parton distributions
of virtual photons at high energy $ep$ colliders is studied in the context of
the DESY-HERA collider. Recently proposed parton densities of virtual photons
are utilized to evaluate the appropriate production processes and their
relevant kinematical regions. It is demonstrated that high $E_T$ jet production
with $E_T\,\simeq 5-7\, {\rm{GeV}}$ and $b\bar{b}$ production can probe the
parton distributions of virtual photons up to virtualities of a few
${\rm{GeV}}^2$. A useful leading order parametrization of our proposed photonic
parton densities, suitable for further studies of these issues, is presented.
