  The thermopower and thermal conductivity of superconducting perovskite
$MgCNi_3$ ($T_c \approx$ 8 K) have been studied. The thermopower is negative
from room temperature to 10 K. Combining with the negative Hall coefficient
reported previously, the negative thermopower definetly indicates that the
carrier in $MgCNi_3$ is electron-type. The nonlinear temperature dependence of
thermopower below 150 K is explained by the electron-phonon interaction
renormalization effects. The thermal conductivity is of the order for
intermetallics, larger than that of borocarbides and smaller than $MgB_2$. In
the normal state, the electronic contribution to the total thermal conductivity
is slightly larger than the lattice contribution. The transverse
magnetoresistance of $MgCNi_3$ is also measured. It is found that the classical
Kohler's rule is valid above 50 K. An electronic crossover occures at $T^* \sim
50 K$, resulting in the abnormal behavior of resistivity, thermopower, and
magnetoresistance below 50 K.
