In 1757 Benjamin Franklin made some astute observations about heat and cold.
Franklin noticed that if he touched the metal lock on his desk, then the wood of the desk, the lock felt colder, even though both were exposed to the same temperature in the room. He concluded that the metal lock felt colder because metal is a better conductor of heat than wood, and drew heat from his hand more than the wood did.
In 1757 Franklin could not have known the real nature of heat. It was not until the 1800s that heat was revealed as random vibration of the atoms that make up all the objects around us. Faster vibration means hotter temperature. Those vibrations are conveyed from hot to cold objects when they touch. On a large scale, however, heat behaves very much like a fluid passed from object to object.
Benjamin Franklin's desk observations demonstrated that metal conducts heat faster than wood. Franklin demonstrated that fact even more dramatically with a silver dollar and a candle. He wrote: "...if you take a dollar between your fingers with one hand, and a piece of wood, of the same dimensions, with the other, and bring both at the same time to the flame of a candle, you will find yourself obliged to drop the dollar before you drop the wood."
