Sanctuaries were erected at these springs by grateful worshippers, and at some of them festivals were held, or they were the resort of pilgrims. As sources of fertility they had a place in the ritual of the great festivals, and sacred wells were visited on Midsummer day, when also the river-gods claimed their human victims. Some of the goddesses were represented by statues or busts in Gallo-Roman times, if not earlier, and other images of them which have been found were of the nature of ex votos, presented by worshippers in gratitude for the goddess's healing gifts. Money, ingots of gold or silver, and models of limbs or other parts of the body which had been or were desired to be healed, were also presented. Gregory of Tours says of the Gauls that they "represent in wood or bronze the members in which they suffer, and whose healing they desire, and place them in a temple."558 Contact of the model with the divinity brought healing to the actual limbs on the principle of sympathetic magic. Many such models have been discovered. Thus in the shrine of Dea Sequana was found a vase with over a hundred; another contained over eight hundred. Inscriptions were engraved on plaques which were fastened to the walls of temples, or placed in springs.559 Leaden tablets with inscriptions were placed in springs by those who desired healing or when the waters were low, and on some the actual waters are hardly discriminated from the divinities. The latter are asked to heal or flow or swell—words which apply more to the waters than to them, while the tablets, with their frank animism, also show that, in some cases, there were many elemental spirits of a well, only some of whom were rising to the rank of a goddess. They are called collectively Niskas—the Nixies of later tradition, but some have personal names—Lerano, Dibona, Dea—showing that they were tending to become separate divine personalities. The Peisgi are also appealed to, perhaps the later Piskies, unless the word is a corrupt form of a Celtic peiskos, or the Latin piscus, "fish."560 This is unlikely, as fish could not exist in a warm sulphurous spring, though the Celts believed in the sacred fish of wells or streams. The fairies now associated with wells or with a water-world beneath them, are usually nameless, and only in a few cases have a definite name. They, like the older spirits of the wells, have generally a beneficent character.561 Thus in the fountains of Logres dwelt damsels who fed the wayfarer with meat and bread, until grievous wrong was done them, when they disappeared and the land became waste.562 Occasionally, however, they have a more malevolent character.563
The spirit of the waters was often embodied in an animal, usually a fish. Even now in Brittany the fairy dweller in a spring has the form of an eel, while in the seventeenth century Highland wells contained fish so sacred that no one dared to catch them.564 In Wales S. Cybi's well contained a huge eel in whose virtues the villagers believed, and terror prevailed when any one dared to take it from the water. Two sacred fish still exist in a holy well at Nant Peris, and are replaced by others when they die, the dead fish being buried.565 This latter act, solemnly performed, is a true sign of the divine or sacred character of the animal. Many wells with sacred fish exist in Ireland, and the fish have usually some supernatural quality—they never alter in size, they become invisible, or they take the form of beautiful women.566 Any one destroying such fish was regarded as a sacrilegious person, and sometimes a hostile tribe killed and ate the sacred fish of a district invaded by them, just as Egyptians of one nome insulted those of another by killing their sacred animals.567 In old Irish beliefs the salmon was the fish of knowledge. Thus whoever ate the salmon of Connla's well was dowered with the wisdom which had come to them through eating nuts from the hazels of knowledge around the well. In this case the sacred fish was eaten, but probably by certain persons only—those who had the right to do so. Sinend, who went to seek inspiration from the well, probably by eating one of its salmon, was overwhelmed by its waters. The legend of the salmon is perhaps based on old ritual practices of the occasional eating of a divine animal. In other cases, legends of a miraculous supply of fish from sacred wells are perhaps later Christian traditions of former pagan beliefs or customs concerning magical methods of increasing a sacred or totem animal species, like those used in Central Australia and New Guinea.568 The frog is sometimes the sacred animal, and this recalls the Märchen of the Frog Bridegroom living in a well, who insisted on marrying the girl who drew its waters. Though this tale is not peculiar to the Celts, it is not improbable that the divine animal guardian of a well may have become the hero of a folk-tale, especially as such wells were sometimes tabu to women.569 A fly was the guardian spirit of S. Michael's well in Banffshire. Auguries regarding health were drawn from its movements, and it was believed that the fly, when it grew old, transmigrated into another.570
Such beliefs were not peculiarly Celtic. They are found in all European folk-lore, and they are still alive among savages—the animal being itself divine or the personification of a divinity. A huge sacred eel was worshipped by the Fijians; in North America and elsewhere there were serpent guardians of the waters; and the Semites worshipped the fish of sacred wells as incarnations or symbols of a god.
Later Celtic folk-belief associated monstrous and malevolent beings with rivers and lakes. These may be the older divinities to whom a demoniac form has been given, but even in pagan times such monstrous beings may have been believed in, or they may be survivals of the more primitive monstrous guardians of the waters. The last were dragons or serpents, conventional forms of the reptiles which once dwelt in watery places, attacking all who came near. This old idea certainly survived in Irish and Highland belief, for the Fians conquered huge dragons or serpents in lochs, or saints chained them to the bottom of the waters. Hence the common place-name of Loch na piast, "Loch of the Monster." In other tales they emerge and devour the impious or feast on the dead.571 The Dracs of French superstition—river monsters who assume human form and drag down victims to the depths, where they devour them—resemble these.
The Each Uisge, or "Water-horse," a horse with staring eyes, webbed feet, and a slimy coat, is still dreaded. He assumes different forms and lures the unwary to destruction, or he makes love in human shape to women, some of whom discover his true nature by seeing a piece of water-weed in his hair, and only escape with difficulty. Such a water-horse was forced to drag the chariot of S. Fechin of Fore, and under his influence became "gentler than any other horse."572 Many Highland lochs are still haunted by this dreaded being, and he is also known in Ireland and France, where, however, he has more of a tricky and less of a demoniac nature.573 His horse form is perhaps connected with the similar form ascribed to Celtic water-divinities. Manannan's horses were the waves, and he was invariably associated with a horse. Epona, the horse-goddess, was perhaps originally goddess of a spring, and, like the Matres, she is sometimes connected with the waters.574 Horses were also sacrificed to river-divinities.575 But the beneficent water-divinities in their horse form have undergone a curious distortion, perhaps as the result of later Christian influences. The name of one branch of the Fomorians, the Goborchinn, means the "Horse-headed," and one of their kings was Eochaid Echchenn, or "Horse-head."