  The phenomenon called the ``sub-Sun'' is the specular reflection of sunlight
by horizontally oriented plates of ice. Although well-known in meteorological
optics, the hydrodynamics of the orientation is not quantitatively understood.
I review the theory of torques on objects at low Reynolds numbers, define
coefficients $C_o$, $C_p$, and $C_\psi$ which describe the orienting torques on
discs, rods, and hexagonal prisms, and report here the results of experiments
to measure $C_o$ and $C_p$.
