his own, is one of the Brythonic equivalents, as already suggested, of the Mac Óc driving his father the Dagda from his house and home, and young Zeus banishing his father Cronus (pp. 147, 151). So we should probably be right in assuming the spring, the tomb, the slab and the tree, to have all belonged to the Celtic Zeus, and that it was he who was originally supposed to give the rain, and to cause the storm of thunder and lightning. An incident of the same kind is related in connection with the story of Owein ab Urien: he was told that, in order to make the Black Knight he desired to encounter come forth to fight with him, he should go to a spot where a large tree overshadowed a well, hard by which lay a marble slab with a silver tankard fastened to it. Owein finds the place, takes up the silver tankard, and dashes water from it with such effect on the slab that it brings on a fearful hail-storm, which strips the tree of all its foliage, and causes wide-spread devastation in the domains of the Black Knight,[1] who in consequence thereof rides forth to avenge himself on the intruder.
Lastly may be mentioned the case of the Snowdonian tarn Dulyn or Black Lake, of which we have an account, published in the year 1805, to the following effect:[2] 'There lies in Snowdon Mountain a lake called Dulyn, in a dismal dingle surrounded by high and dangerous rocks: the lake is exceedingly black, and its fish are loathsome, having large heads and small bodies. No wild swan or duck or any kind of bird has ever been seen to light on it, as is their wont on every other Snow-
