+309+. Water is abundantly employed in religious ritual as a means of purification from ceremonial defilement, and in services of initiation. A bathing-place often stood by a shrine (as in pre-Islamic Arabia and in Islam now), and immersions came to play a prominent part in highly developed systems (Jewish, Christian, Mithraic). The purification was generally symbolic, but in some forms of Christian belief the water of baptism is held to have regenerating power[577]--a survival of the ancient conception of the divinity of water. +310+. It is often hard to say whether a body of water is regarded simply as itself a living thing, or is conceived of as the dwelling place of an isolated or independent spirit. In savage systems the details on this point are hardly ever recorded or obtainable; but the beliefs involved in later folk-lore make it probable that this latter stage of the construction of creeds is passed through in savage life. The water maidens of Greek mythology and the Germanic nixies and water kelpies are developed forms of spirits. Sacred springs and wells are still believed to be inhabited by beings that are not gods, but possess superhuman power. +311+. While wells and streams of a domestic character (such as are freely used by human beings) are generally friendly, they have their unfriendly side. The spirits that dwell in them are sometimes regarded as being hostile to man. They drag the incautious wanderer into their depths, and then nothing can save him from drowning. Fear of these malignant beings sometimes prevents attempts to rescue a drowning person; such attempts are held to bring down the vengeance of the water-demon on the would-be rescuer.[578] +312+. In the course of time true water-gods appear. In Greece every river had its deity, and in India such deities are found in the Mahabharata.[579] When in the Iliad the river Xanthos rises to seize and drown Achilles, it may be a question whether the stream or the god of the stream is the actor. Nor is it always possible to say whether the extrahuman Power inhabiting a water mass is a true god or a spirit; the latter form may pass by invisible gradations into the former. +313+. Waters originally divine tend to become the abodes of the deity of the place, or sacred to him, and healing or other power is ascribed to his presence or agency.[580] Sacred water, being unwilling to retain anything impure, thus becomes a means of detecting witches and other criminals, who, when thrown in, cannot sink, but are rejected by the divine Power.