It is the passage of heat from one body to another which it touches, or from one particle of a body to another particle of the same body. What bodies are good conductors of heat? Such bodies as gold, platinum, copper, silver, iron, zinc, tin, and lead, in the order named, are the best conductors of heat. What bodies are poor conductors of heat? Such bodies as glass, wood, charcoal, wool, hair, and fur. Fur is the poorest conductor of heat known. Why does a piece of wood blazing at one end not feel hot at the other end? Because wood is a poor conductor, and the heat goes slowly through it. Why does a piece of iron feel cold in winter? Because the iron is a good conductor, and carries the heat away from our hands very rapidly. Why does fur feel warmer than iron in the winter? Because the fur is a poor conductor, and carries the heat away from our hands very slowly. Why does a wooden pump-handle seem less cold than one of iron? Because wood is not so good a conductor as iron; hence, it does not carry the heat of our hands away so rapidly. Why does carpet seem warmer than the bare floor? Because the carpet is a poorer conductor than the wood of the floor, and does not carry away the heat of our bodies so rapidly. Why does a stone pavement make our feet cold in winter? Because the stone is a good conductor, and rapidly carries the heat away from our feet. Why does heated iron feel hot to us? Because the iron is a good conductor, and gives off its heat rapidly to our bodies. Why does a piece of cloth, when heated, not feel hot? Because the cloth is a poor conductor, and gives off its heat very slowly. Why will a block of wood, when heated, remain hot longer than a heated brick? Because wood is a poorer conductor than brick, and does not give off its heat so rapidly. Why is a block of wood better than iron or brick, to keep our feet warm while on a journey? Because it does not give off its heat so rapidly, and therefore remains warm longer than iron or brick. Why should the wood or brick be wrapped in cloth? Because the cloth, being a poor conductor, helps to keep the heat from passing off so rapidly. Why does iron feel colder than water when both are at the same temperature? Because iron is a better conductor than water, and carries away the heat from our hands more rapidly. Are liquids good conductors of heat? No; liquids are poor conductors of heat. Is air a good conductor of heat? No; air is a poor conductor of heat. Are gases as good conductors as liquids? No; gases are poorer conductors than liquids. Why is water a better conductor than air? Because the particles of water are closer together than the particles of air. Why is iron a better conductor than water? Because the particles of iron are closer together than the particles of water. How do we know that water is a poor conductor of heat?