  The McCoy-Roan integral representation for gaps of the integrable Z_n-
symmetric Chiral Potts quantum chain is used to calculate the boundary of the
incommensurable phase for various n. In the limit n -> \infty an analytic
formula for this phase boundary is obtained. The McCoy-Roan formula gives the
gaps in terms of a rapidity. For the lowest gap we conjecture the relation of
this rapidity to the physical momentum in the high-temperature limit using
symmetry properties and comparing the McCoy-Roan formula to high-temperature
expansions and finite-size data.
