  The summational invariant and the corresponding local Maxwellian that are
compatible with the Enskog equation are discussed, with special interest in the
presence of a boundary. The local Maxwellian corresponding to the summational
invariant is restrictive compared to the case of the Boltzmann equation in the
sense that a radial flow and time-dependent temperature are forbidden. However,
a rigid body rotation with a constant angular velocity is admitted as in the
case of the Boltzmann equation. The influence of the presence of a boundary is
also discussed in simple situations.
