There has always been a mystery connected with the origin and use of fire, which has led to many myths. Thus, the Greeks insisted that Prometheus, in order to perform a great service to humanity, stole fire from heaven and gave it to man. For this crime against the authority of the gods, he was chained to a rock to suffer the torture of the vulture who pecked at his vitals. Aeschylus has made the most of this old legend in his great drama of _Prometheus Bound_. Nearly every tribe or nation has some tradition regarding the origin of fire. Because of its mystery and its economic value, it was early connected with religion and made sacred in many instances. It was thus preserved at the altar, never being allowed to become extinct without the fear of dire calamity. Perhaps the economic and religious ideas combined, because tribes in travelling from place to place exercised great care to preserve it. The use of fire in worship became almost universal among tribes and ancient nations. Thus the Hebrews and the Aryans, including Greeks, Romans, and Persians, as well as the Chinese and Japanese, used fire in worship. Among other tribes it was worshipped as a symbol or even as a real deity. Even in the Christian religion, the use of the burning incense may have some psychological connection with the idea of purification through fire. Whether its mysterious nature led to its connection with worship, and the superstition connected with its continued burning, or whether from economic reasons it became a sacred matter, has never been determined. The custom that a fire should never go out upon the altar, and that it should be carried in migrations from place to place, would seem to indicate that these two motives were closely allied, if not related in cause and effect. {90} Evidently, fire was used for centuries before man invented methods of reproducing it. Simple as the process involved, it was a great invention; or it may be stated that many devices were resorted to for the creation of artificial fire. Perhaps the earliest was that of rubbing two pieces of dry wood together, producing fire by friction. This could be accomplished by persistent friction of two ordinary pieces of dry wood, or by drilling a hole in a dry piece of wood with a pointed stick until heat was developed and a spark produced to ignite pieces of dry bark or grass. Another way was to make a groove in a block of wood and run the end of a stick rapidly back and forth through the groove. An invention called the fire-drill was simply a method of twirling rapidly in the hand a wooden drill which was in contact with dry wood, or by winding a string of the bow several times around the drill and moving the bow back and forth horizontally, giving rapid motion to the drill.