Whatever their locally accepted causes of being may be, it is beyond any question that in the fairy folk-lore of Wales, as of other lands, are to be found the _débris_ of ancient mythology--scintillant fragments of those magic constellations which glow in the darkness of primeval time, grand and majestic as the vast Unknown out of which they were evolved by barbaric fancy. Through the aid of modern scientific research, 'those ages which the myths of centuries have peopled with heroic shadows'[63] are brought nearer to us, and the humble Welsh Tylwyth Teg may reach back and shake hands with the Olympian gods.