Wood and Metal Cylinder

Comprising a cylinder 200 x 30 mm diameter one-half of which is wood, the other metal Comprising a cylinder 200 x 30 mm diameter one-half of which is wood, the other metal. If paper is wrapped tightly round the cylinder and the rod is held above the flame, the portion is contact with the wood will be quickly scorched while the portion in contact with the metal will remain uncharred.