When placed on the inclined plane, this wooden cylinder tends to roll upward, coming to a halt at a well-determined position. Because of this apparently absurd phenomenon, the apparatus (like the climbing cone inv. 3387) was classified as a "mechanical paradox." Actually, the cylinder conceals a metal ballast that shifts the center of gravity away from the central axis. This mass thus creates a mechanical couple that offsets the action of the gravitational force, enabling the cylinder to move some way up an inclined plane and come to a stop. Provenance: Lorraine collections.