  From the Boltzmann equation Chapman and Cowling have firstly motivated a
hierarchy of differential equations. I consider a general version of these
differential equations which contain the Navier-Stokes system. In the paper I
derive a relativistic version of these partial differential equations. This is
interesting because in the derivation a covariant version of a time direction
is used. This time direction is needed to derive a reduction of the
differential equations.
