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We have mapped the velocity structure of the cometary compact HII regionG29.96-0.02 using long-slit echelle spectra of the HI Br gamma line. Thistechnique detects line emission over a much wider area at the necessary spatialresolution compared to radio recombination line observations. Significantstructure in both the velocity centroids and the line widths is seen over theentire nebula. Large line widths are seen ahead of the bow and in the tailwhich may be due to turbulent motions in shocked and interface regionsrespectively. We construct analytic models of the density and velocitystructure in order to attempt to distinguish between the bow shock andchampagne flow models which have been put forward to explain the cometarymorphology of many compact HII regions. The bow shock model is unable toexplain the large velocity gradient that we see right across the tail of thecometary region which can only be explained by the streaming motions towardslow density regions in the champagne model. However, our approximation to thechampagne model is also not able to fit all of the features of the data. Morerealistic versions of this model which include the effects of stellar winds anddensity gradients may be able to provide a better match to these data.Comment: 19 pages Latex source, 9 postscript figures and macros. gzipped tar  set. To appear in Astrophysical Journal, June 20. Also available by anonymous  ftp from ftp://aaoepp.aao.gov.au/local/sll/g29.uu (uuencoded gzipped tar  file

An Infrared Study of the Velocity Structure of the Cometary Compact H II Region G29.96-0.02