  We report on the observation of a quenched moment of inertia as resulting
from superfluidity in a strongly interacting Fermi gas. Our method is based on
setting the hydrodynamic gas in slow rotation and determining its angular
momentum by detecting the precession of a radial quadrupole excitation. The
measurements distinguish between the superfluid or collisional origin of
hydrodynamic behavior, and show the phase transition.
