  I report the detection of circular polarisation, associated with relativistic
ejections, from the `microquasar' GRS 1915+105. I further compare detections
and limits of circular polarisation and circular-to-linear polarisation ratios
in other X-ray binaries. Since in at least two cases the dominance of linear
over circular polarisation or vice versa is a function of frequency, this seems
to indicate that this is a strong function of depolarisation in the source.
Furthermore, I note that circular polarisation has only been detected from
sources whose jets lie close to the plane of the sky, whereas we have quite
stringent limits on the circular polarisation of jets which lie close to the
line of sight.
