He lit a little Bunsen burner and melted some Wood's metal over it while the detective and the residents watched. (Wood's metal is an alloy of bismuth, lead, tin, and cadmium that has a low melting point of 71°C.) Then he selected a wound in the victim' s chest above the location of the liver and poured the liquid metal into it. The metal slid down through the wound into the punctured liver. When it was cool he removed an exact molf of the tip of the murder weapon. He added the length of this tip to the distance between the liver and the skin surface of the chest. Then he said to the homicide detective, "It' s a knife five and a half inches long, one inch wide and one sixteenth of an inch thick.