  Standard, planar accretion discs operate through a dissipative mechanism,
usually thought to be turbulent, and often modelled as a viscosity. This acts
to take energy from the radial shear, enabling the flow of mass and angular
momentum in the radial direction. In a previous paper we discussed
observational evidence for the magnitude of this viscosity, and pointed out
discrepancies between these values and those obtained in numerical simulations.
In this paper we discuss the observational evidence for the magnitude of the
dissipative effects which act in non--planar discs, both to transfer and to
eliminate the non--planarity. Estimates based on the model by Ogilvie (1999),
which assumes a small--scale, isotropic viscosity, give alignment timescales
for fully ionized discs which are apparently too short by a factor of a few
compared with observations, although we emphasize that more detailed
computations as well as tighter observational constraints are required to
verify this conclusion. For discs with low temperature and conductivity, we
find that the timescales for disc alignment based on isotropic viscosity are
too short by around two orders of magnitude. This large discrepancy suggests
that our understanding of viscosity in quiescent discs is currently inadequate.
