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."[610] 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.[611] 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."[612] 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.[613] 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.[614] Occasionally, however, they have a more malevolent character.[615]