  In this paper, high quality spectropolarimetric observations of the
Wolf-Rayet (WR) Star WR1 (HD4004) obtained with ESPaDOnS at CFHT are presented.
All major emission lines present in the spectrum show depolarization in the
relative Stokes parameters Q/I and U/I. From the behaviour of the amount of
line depolarization as a function of line strength, the intrinsic continuum
light polarization of WR1 is estimated to be P/I=0.443 \pm 0.028 % with an
angle of \theta=-26.2^o.
  Although such a level of polarization could in principle be caused by a wind
flattened by fast rotation, the scenario in which it is a consequence of the
presence in the wind of Corotating Interaction Regions (CIRs) is preferred.
This is supported by previous photometric and spectroscopic observations
showing periodic variations with a period of 16.9 days. This is now the third
WR star thought to exhibit CIRs in its wind that is found to have line
depolarization. Previous authors have found a strong correlation between line
depolarization and the presence of an ejected nebula, which they interpret as a
sign that the star has reached the WR phase relatively recently since the
nebula are thought to dissipate very fast. In the cases where the presence of
CIRs in the wind is favoured to explain the depolarization across spectral
lines, the above mentioned correlation may be indicating that those massive
stars have only very recently transited from the previous evolutionary phase to
the WR phase.
