Torus mapping yields constants of motion for stars trapped at a resonance .
Each such constant of motion yields a system of contours in velocity space at the Sun and neighbouring points .
If Jeans ’ theorem applied to resonantly trapped orbits , the density of stars in velocity space would be equal at all intersections of any two contours .
A quantitative measure of the violation of this principal is defined and used to assess various pattern speeds for a model of the bar recently fitted to observations of interstellar gas .
Trapping at corotation of a bar with pattern speed in the range 33 - 36 \mathrm { Gyr } ^ { -1 } is favoured and trapping at the outer Lindblad resonance is disfavoured .
As one moves around the Sun the structure of velocity space varies quite rapidly , both as regards the observed star density and the zones of trapped orbits .
The data seem consistent with trapping at corotation .