Fire

Fire, heat and light resulting from the rapid combination of oxygen, or in some cases gaseous chlorine, with other materials. The light is in the form of a flame, which is composed of glowing particles of the burning material and certain gaseous products that are luminous at the temperature of the burning material. The conditions necessary for the existence of fire are the presence of a combustible substance, a temperature high enough to cause combustion (called the ignition temperature) and the presence of enough oxygen (usually provided by the air) or chlorine to enable rapid combustion to continue.

Fire has been produced by two principal methods, friction and percussion. In the friction method, friction raises the temperature of a combustible material (kindling) to ignition temperature. The percussion method produces a spark to set kindling afire.

In some cultures people have used and still use chiefly the friction method, in which two pieces of wood surrounded by combustible material are rubbed together until the ignition temperature is reached. In the stick-and-groove method, a stick is rubbed in a groove in another piece of wood. In the fire-drill method, a stick is rotated rapidly in a pit in a stationary piece of wood. The stick is rotated by rubbing it between the palms of the hands or by moving back and forth a wooden bow whose string is wrapped around the stick.

The most basic percussion method of producing fire is striking together two pieces of flint, or by striking flint against pyrite. Later, steel was substituted for the pyrite. The flint-and-steel method prevailed throughout the civilized world until about 1827, when matches came into use. With matches, friction is used to heat the tip of the match to the point at which chemicals in the match head ignite.

Fire may also be produced by using a lens or curved reflector to concentrate the rays of the Sun on combustible material.

The use of fire probably developed in four stages. First, people observed about them natural sources of fire, such as volcanoes and trees set afire by lightning. Second, they acquired fire from natural sources and used it for warmth, light, and protection from predators. Third, they learned to make fire whenever they chose. Finally, they learned to control fire for use in smelting metal ore, in baking pottery, and in numerous other ways to help create new technologies and make life more comfortable.

The keeping and use of fire probably had an influence in ending nomadism and consequently influenced the development of the social and political institutions connected with members of a society having a permanent home.