_The Discovery and Use of Fire_.--The use of fire was practised in the early history of man. Among the earliest records in caves are found evidences of the use of fire. Charcoal is practically indestructible, and, although it may be crushed, the small particles maintain their shape in the clays and sands. In nearly all of the relics of man discovered in caves, the evidences of fire are to be found, and no living tribe has yet been discovered so low in the scale of life as to be without the knowledge of fire and probably its simple uses, although a few tribes have been for the time being without fire when first discovered. This might seem to indicate that at a very early period man did not know how to create fire artificially, but carried it and preserved it in his wanderings. There are indications that a certain individual was custodian of the fire, and later it was carried by the priest or _cacique_. Here, as in other instances in the development of the human race, an economic factor soon assumes a religious significance, and fire becomes sacred. There are many conjectures respecting the discovery of fire. Probably the two real sources are of lightning that struck forest trees and set them on fire and the action of volcanoes in throwing out burning lava, which ignited combustible material. Either one or the other, and perhaps both, of these methods may have furnished man with fire. Others have suggested that the rubbing together of dead limbs of trees in the forests after they were moved by the winds, may have created fire by friction. It is possible, also, that the sun's rays may have, when concentrated on combustible {89} material, caused spontaneous ignition. The idea has been advanced that some of the forest fires of recent times have been ignited in this way. However, it is evident that there are enough natural sources in the creation of fire to enable tribes to use it for the purposes of artificial heat, cooking, and later, in the age of metals, of smelting ores.