  We use APEX mapping observations of 13CO, and C18O (2-1) to investigate the
internal gas kinematics of the filamentary cloud G350.54+0.69, composed of the
two distinct filaments G350.5-N and G350.5-S. G350.54+0.69 as a whole is
supersonic and gravitationally bound. We find a large-scale periodic velocity
oscillation along the entire G350.5-N filament with a wavelength of ~1.3 pc and
an amplitude of ~0.12 km/s. Comparing with gravitational-instability induced
core formation models, we conjecture that this periodic velocity oscillation
could be driven by a combination of longitudinal gravitational instability and
a large-scale periodic physical oscillation along the filament. The latter may
be an example of an MHD transverse wave. This hypothesis can be tested with
Zeeman and dust polarization measurements.
