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It is well known that the existence of H~I and CO gas at ``forbidden'' velocities in longitude-velocity (\lv) diagrams of the inner Galaxy (e.g. Liszt \& Burton 1980) is inconsistent with circular motion in an axisymmetric potential. Gas flow in a barred potential could be consistent with the observations, however. This kinematic data provides us with a probe of the mass distribution in the Galactic bulge which is unaffected by extinction. We have compared the observations to 2-D hydrodynamical simulations of gas flows in a family of barred potentials; the gas flow pattern is very sensitive to the assumed potential.
We present a model, with a bar with semimajor axis 3 kpc, axis ratio 4:1, and pattern speed 55 \kmskpc, which reproduces the extreme-velocity envelope of the H~I \lv\ diagram reasonably well, if the bar is viewed at 35\deg\ to its major axis. We argue that models with the bar more end--on than $\sim 25\deg$ cannot reproduce the emission in the forbidden quadrants of the H~I \lv\ diagram.
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