There is a tremendous literature[53] dealing with the folklore of holy wells and streams. The number of holy wells and streams in Britain is legion; there are 3,000 in Ireland alone, and the first thing which strikes us in a casual study of the folklore is the close association of the wells with sacred trees. Almost equally distinctly we gather that both were situated near holy stones, and that the worship included ceremonials connected with all three. The folklore dealing with holy wells and well-worship is so various that it will be useful for our present purpose to classify the portions we need under the following headings. 1. Well-worship outcome of pre-Christian days and customs. 2. Wells generally situated near circles, dolmens, cromlechs or cairns, or churches which have replaced them. 3. Association with sacred trees. 4. Well-worship and offerings. 5. Time of the chief festivals. 1. _Pagan origin._--It seems to be accepted now that well-worship in Britain originated long before the Christian era; that it was not introduced by the Christian missionaries, but rather they found it in vogue on their arrival, and tolerated it at first and utilized it afterwards, as they did a great many other Pagan customs. With regard to this point Wood-Martin writes:[54] “In many Irish MSS. there are allusions to this pre-Christian worship. For example, Tirehan relates that St. Patrick, in his progress through Ireland, came to a fountain called Slaun, to which the Druids offered sacrifices, and which they worshipped as a God; and in Adamnan’s _Life of St. Columkille_ it is recounted that this saint, when in the country of the Picts, heard of a notable fountain to which the Pagans paid divine honour.” He adds (p. 50): “It evidently did not originate in the blessing of wells by early saints and thus spread downwards, until it became almost, if not quite, universal; on the contrary, it began from the people, who were being Christianized, and thence permeated the entire system of Irish Christianity.” Baring-Gould tells us much concerning the transitional state (pp. 28 _et seq._). Wood-Martin divides holy wells into three classes: (1) those which “derive their reputed virtues from Pagan superstition”; (2) those which were “transferred from Pagan to so-called Christian uses,” and (3) “a few which may lay claim to a merely Christian origin.”[55] It is very easy to understand how the purely devout custom developed in course of time, in the case of some wells at any rate, into a more superstitious one, how some wells came to be called “wishing-wells” and others were regarded as prophetic. Rhys gives us several instances of these two classes in Wales.[56] Wishing-wells are known all over the United Kingdom; many authors give accounts of them.[57]