  We present a perturbation solution for a pressure-driven fluid flow in a
rotating toroidal channel. The analysis shows the difference between the
solutions of full and simplified equations studied earlier. The result is found
to be reliable for {\it low} Reynolds number ($\R$) as was the case for a
previously studied solution for high $\R$. The convergence conditions are
defined for the whole range of governing parameters. The viscous flow exhibits
some interesting features in flow pattern and hydrodynamic characteristics.
