  We report on full-polarization radio observations of the Perseus cluster
(Abell 426) using the Westerbork Synthesis Radio Telescope (WSRT) at
wavelengths from 81-95 cm. We have employed a novel technique, Rotation Measure
synthesis (Brentjens and de Bruyn, 2005) to unravel the polarization properties
of the emission across the full field of view and detect polarized emission
over a wide range of RM from about 0 to 90 rad m^-2. The low RM emission is
associated with our Galaxy, while the high RM emission is associated with the
Perseus cluster. The latter reaches typical surface brightness levels of 0.5-1
mJy per beam and must be rather highly polarized. Most of the peripheral
polarized emission appears too bright, by about 1-2 orders of magnitude, to be
explainable as Thomson scattered emission of the central radio source off the
thermal electrons in the cluster. The bulk of the emission associated with the
Perseus cluster is probably related to buoyant bubbles of relativistic plasma,
probably relics from still active or now dormant AGN within the cluster. A
lenticular shaped structure measuring 0.5-1 Mpc is strikingly similar to the
structures predicted by Ensslin et al. (1998). At the western edge of the
cluster, we detect very long, linear structures that may be related to shocks
caused by infall of gas into the Perseus cluster.
