  Optical linear polarimetry of 8 ultra cool field dwarfs, with spectral types
ranging from M9 to L8, is presented. The linear polarisation, P, of each dwarf
we measured is P < 0.2%. Three dwarfs have polarisations compatible with zero,
two are marginal detections, and three have significant polarisation. Due to
their small distance, an insterstellar origin for the detected polarisation can
be safely ruled out. Our detections confirm that dust is present in the
atmosphere of these brown dwarfs and that the scattering geometry is not
symmetric. Possibilities for asymmetry include the dwarfs rotating rapidly and
being oblate, or the cloud coverage in the atmosphere being inhomogenous.
