  We probe the secondary rheology of granular media, by imposing a main flow
and immersing a vane-shaped probe into the slowly flowing granulate. The
secondary rheology is then the relation between the exerted torque T and
rotation rate \omega of our probe. In the absence of any main flow, the probe
experiences a clear yield-stress, whereas for any finite flow rate, the yield
stress disappears and the secondary rheology takes on the form of a double
exponential relation between \omega and T. This secondary rheology does not
only depend on the magnitude of T, but is anisotropic --- which we show by
varying the relative orientation of the probe and main flow. By studying the
depth dependence of the three characteristic torques that characterize the
secondary rheology, we show that for counter flow, the dominant contribution is
frictional like --- i.e., T and pressure are proportional for given \omega ---
whereas for co flow, the situation is more complex. Our experiments thus reveal
the crucial role of anisotropy for the rheology of granular media.
