  We study hydrodynamic slowing-down of a particle moving in a temperature
gradient perpendicular to a wall. At distances much smaller than the particle
radius, $h\ll a$, lubrication approximation leads to the reduced velocity
$u/u_{0}=3\frac{h}{a}\ln \frac{a}{h}$, with respect to the bulk value $u_{0}$.
With Brenner's result for confined diffusion, we find that the trapping
efficiency, or effective Soret coefficient, increases logarithmically as the
particle gets very close to the wall. This provides a quantitative explanation
for the recently observed enhancement of thermophoretic trapping at short
distances. Our discussion of parallel and perpendicular thermophoresis in a
capillary, reveals a very a good agreement with five recent experiments on
charged polystyrene particles.
