  We have mapped the velocity structure of the cometary compact HII region
G29.96-0.02 using long-slit echelle spectra of the HI Br gamma line. This
technique detects line emission over a much wider area at the necessary spatial
resolution compared to radio recombination line observations. Significant
structure in both the velocity centroids and the line widths is seen over the
entire nebula. Large line widths are seen ahead of the bow and in the tail
which may be due to turbulent motions in shocked and interface regions
respectively. We construct analytic models of the density and velocity
structure in order to attempt to distinguish between the bow shock and
champagne flow models which have been put forward to explain the cometary
morphology of many compact HII regions. The bow shock model is unable to
explain the large velocity gradient that we see right across the tail of the
cometary region which can only be explained by the streaming motions towards
low density regions in the champagne model. However, our approximation to the
champagne model is also not able to fit all of the features of the data. More
realistic versions of this model which include the effects of stellar winds and
density gradients may be able to provide a better match to these data.
