  We relate the frequency of the scissors mode to the moment of inertia of a
trapped Bose gas at finite temperature in a semi-classical approximation. We
apply these theoretical results to the data obtained in our previous study of
the properties of the scissors mode of a trapped Bose-Einstein condensate of
$^{87}$Rb atoms as a function of the temperature. The frequency shifts that we
measured show quenching of the moment of inertia of the Bose gas at
temperatures below the transition temperature - the system has a lower moment
of inertia that of a rigid body with the same mass distribution, because of
superfluidity.
