  We show that gamma ray line emission at $\sim$0.4 MeV and $\lsim 0.2$ MeV can
be produced by Compton scattering of beamed radiation in the jets of Galactic
black hole candidates. This mechanism has the novel feature of not invoking the
presence of $e^+$--$e^-$ pairs. To produce the two lines we employ a symmetric
double sided jet with bulk flow velocity of about 0.5 c and incident beam
radiation with a hard energy spectrum. We show that the two lines can be seen
at viewing angle cosines relative to the jet ranging from 0.2 to 0.6. This
comprises 40\% of the total solid angle. In addition, the line radiation is
approximately 10\% polarized. Depending on the bulk flow and viewing angle the
model can produce lines at other energies as well. In particular a broad
feature near 1 MeV can be seen by viewing the jet close to its axis. Our model
can also accommodate single line spectra if the beamed gamma ray emission or
the jets themselves are asymmetric.
