  In relativistic gravity, a spinning pulsar will precess as it orbits a
compact companion star. We have measured the effect of such precession on the
average shape and polarization of the radiation from PSR B1534+12. We have also
detected, with limited precision, special-relativistic aberration of the
revolving pulsar beam due to orbital motion. Our observations fix the system
geometry, including the misalignment between the spin and orbital angular
momenta, and yield a measurement of the precession timescale consistent with
the predictions of General Relativity.
