When Epeiros had been thus thickly sprinkled with settlements, an earthquake appears to have produced in the range of Pelion the narrow precipitous gap, afterwards known as Tempe, by which the waters of the Thessalian lake discharged themselves into the sea. This happened, we are told, while one Pelasigos[33] reigned over the mountaineers in the district of Hæmonia. They were celebrating a great feast, when a certain slave named Peloros, brought them tidings of what had come to pass, speaking with admiration of the vast plains which were appearing through the ebbing waters. In gratitude for the news he communicated, they caused the man to seat himself at table while both the king and his attendants, in the joy and fulness of their hearts ministered to him. This, it is said, was the origin of the Pelorian festival, afterwards, down to a very late period, celebrated with great pomp and magnificence in Thessaly, where, for the day, masters changed condition with their slaves, and became their servants.[34] The same festival in the Pelasgian settlements of Italy was known down to the latest times, under the name of Saturnalia. Footnote 33: Palmer. Exercit. p. 527.—Sch. Apoll. Rhod. i. 500.—Dion. Hal. i. 3. 1. Footnote 34: Athen. xiv. 45. On the interior of Thessaly becoming thus habitable, the Pelasgian tribes of Epeiros, beginning to be straitened for room, and feeling still the original wandering impulse, poured over the heights of Pindos into the valleys of Histiæotis, and moved eastward along the foot of the Cambunian mountains, settling every where as they advanced. The tribe which took this direction bore the name of Perrhæbians, and left traces of their movements in the great Perrhæbian forest, stretching to the foot of Olympos, and in the name of the whole district extending from the Peneios to the northern limits of Thessaly. In this rich and fertile tract they became powerful, spreading their dominion along the banks of the Peneios, quite down to the sea. But the Lapithæ rising into consequence and overcoming the Perrhæbians in battle, reduced a portion of the tribes under their yoke, while the remainder, enamoured of independence, retreated inland, again crossed the Pindos, and established themselves in the upper valley of the Acheloös. About the same time, perhaps, a fragment of this tribe traversing the whole of Thessaly crossed over into Eubœa, where they subdued and took possession of Histiæotis. It was possibly the entrance of these adventurers into the island, pushing fresh waves of population southward, that caused the contest for the Lalantian plain, and the emigration of the Curetes to the continent.