Certain waters had the power of ejecting the demon of madness.  Besides drinking, the patient was thrown into the waters, the shock being intended to drive the demon away, as elsewhere demons are exorcised by flagellation or beating.  The divinity of the waters aided the process, and an offering was usually made to him.  In other cases the sacred waters were supposed to ward off disease from the district or from those who drank of them.  Or, again, they had the power of conferring fertility.  Women made pilgrimages to wells, drank or bathed in the waters, implored the spirit or saint to grant them offspring, and made a due offering.[652] Spirit or saint, by a transfer of his power, produced fruitfulness, but the idea was in harmony with the recognised power of water to purify, strengthen, and heal.  Women, for a similar reason, drank or washed in the waters or wore some articles dipped in them, in order to have an easy delivery or abundance of milk.[653]

The waters also gave oracles, their method of flowing, the amount of water in the well, the appearance or non-appearance of bubbles at the surface when an offering was thrown in, the sinking or floating of various articles, all indicating whether a cure was likely to occur, whether fortune or misfortune awaited the inquirer, or, in the case of girls, whether their lovers would be faithful.  The movements of the animal guardian of the well were also ominous to the visitor.[654] Rivers or river divinities were also appealed to.  In cases of suspected fidelity the Celts dwelling by the Rhine placed the newly-born child in a shield on the waters.  If it floated the mother was innocent; if it sank it was allowed to drown, and she was put to death.[655] Girls whose purity was suspected were similarly tested, and S. Gregory of Tours tells how a woman accused of adultery was proved by being thrown into the Saone.[656] The mediaeval witch ordeal by water is connected with this custom, which is, however, widespread.[657]

The malevolent aspect of the spirit of the well is seen in the “cursing wells” of which it was thought that when some article inscribed with an enemy’s name was thrown into them with the accompaniment of a curse, the spirit of the well would cause his death.  In some cases the curse was inscribed on a leaden tablet thrown into the waters, just as, in other cases, a prayer for the offerer’s benefit was engraved on it.  Or, again, objects over which a charm had been said were placed in a well that the victim who drew water might be injured.  An excellent instance of a cursing-well is that of Fynnon Elian in Denbigh, which must once have had a guardian priestess, for in 1815 an old woman who had charge of it presided at the ceremony.  She wrote the name of the victim in a book, receiving a gift at the same time.  A pin was dropped into the well in the name of the victim, and through it and through knowledge of his name, the spirit of the well acted upon him to his hurt.[658] Obviously rites like these, in which magic and religion mingle, are not purely Celtic, but it is of interest to note their existence in Celtic lands and among Celtic folk.