  We report experimental observations obtained by particule image velocimetry
(PIV) of the behavior of a flow driven by rotation and precession of a
cylindrical container. Various hydrodynamical regimes are identified according
to the value of the control parameter which is the ratio of the precession
frequency to the rotation frequency. In particular when this parameter is
increased from small values, we have observed an induced differential rotation
followed by the apparition of permanent cyclonic vortices.
