The resistance against rolling of a rigid cylinder on a flat Viscous surfac
e is investigated. We found that the rolling-friction coefficient reveals s
trongly non-linear dependence on the cylinder's velocity. For low velocity
the rolling-friction coefficient rises with velocity due to increasing defo
rmation rate of the surface. For larger velocity, however, it decreases wit
h velocity according to decreasing contact area and deformation of the surf
ace.