Experience proves that cast and wrought iron can be obtained with auv ore of iron, but that the cast and wrought iron produced have various properties because of the greater or less purity of the ores, and because the methods of treatment do not all effect the elimination of foreign substances to an equal degree. According to circumstances, a metal will be obtained more or less tenacious or brittle, hard or soft, pure or impure. But none the less will the names cast and wrought iron be given to the extremes produced. For the same reason we should call every intermediate product, which is neither wrought nor cast iron, steel, whatever its degree of purity may be. The crude cast product resulting from the reduction of the ores of iron may be called pig iron. It is an impure iron which is not malleable, at least when heated, but which mav be tempered by being suddenly cooled.